package mcp
Import Path
github.com/mark3labs/mcp-go/mcp (on go.dev)
Dependency Relation
imports 12 packages, and imported by 3 packages
Involved Source Files
consts.go
errors.go
prompts.go
resources.go
tasks.go
tools.go
typed_tools.go
Package mcp defines the core types and interfaces for the Model Context Protocol (MCP).
MCP is a protocol for communication between LLM-powered applications and their supporting services.
utils.go
Package-Level Type Names (total 151)
Annotated is the base for objects that include optional annotations for the
client. The client can use annotations to inform how objects are used or
displayed
Annotations *Annotations
Describes who the intended customer of this object or data is.
It can include multiple entries to indicate content useful for multiple
audiences (e.g., `["user", "assistant"]`).
ISO 8601 formatted timestamp (e.g., "2025-01-12T15:00:58Z")
Describes how important this data is for operating the server.
A value of 1 means "most important," and indicates that the data is
effectively required, while 0 means "least important," and indicates that
the data is entirely optional.
Priority ranges from 0.0 to 1.0 (1 = most important, 0 = least important).
func ParseAnnotations(data map[string]any) *Annotations
ArgumentOption is a function that configures a PromptArgument.
It allows for flexible configuration of prompt arguments using the functional options pattern.
func ArgumentDescription(desc string) ArgumentOption
func RequiredArgument() ArgumentOption
func WithArgument(name string, opts ...ArgumentOption) PromptOption
AudioContent represents the contents of audio, embedded into a prompt or tool call result.
It must have Type set to "audio".
Annotated Annotated
Annotated.Annotations *Annotations
The base64-encoded image data.
The MIME type of the image. Different providers may support different image types.
Meta is a metadata object that is reserved by MCP for storing additional information.
// Must be "image"
AudioContent : Content
func AsAudioContent(content any) (*AudioContent, bool)
func NewAudioContent(data, mimeType string) AudioContent
A base64-encoded string representing the binary data of the item.
The MIME type of this resource, if known.
Raw per‑resource metadata; pass‑through as defined by MCP. Not the same as mcp.Meta.
Allows _meta to be used for MCP-UI features for example. Does not assume any specific format.
The URI of this resource.
BlobResourceContents : ResourceContents
func AsBlobResourceContents(content any) (*BlobResourceContents, bool)
CallToolRequest is used by the client to invoke a tool provided by the server.
// HTTP headers from the original request
Params CallToolParams
Request Request
Request.Method string
BindArguments unmarshals the Arguments into the provided struct
This is useful for working with strongly-typed arguments
GetArguments returns the Arguments as map[string]any for backward compatibility
If Arguments is not a map, it returns an empty map
GetBool returns a bool argument by key, or the default value if not found
GetBoolSlice returns a bool slice argument by key, or the default value if not found
GetFloat returns a float64 argument by key, or the default value if not found
GetFloatSlice returns a float64 slice argument by key, or the default value if not found
GetInt returns an int argument by key, or the default value if not found
GetIntSlice returns an int slice argument by key, or the default value if not found
GetRawArguments returns the Arguments as-is without type conversion
This allows users to access the raw arguments in any format
GetString returns a string argument by key, or the default value if not found
GetStringSlice returns a string slice argument by key, or the default value if not found
RequireBool returns a bool argument by key, or an error if not found or not convertible to bool
RequireBoolSlice returns a bool slice argument by key, or an error if not found or not convertible to bool slice
RequireFloat returns a float64 argument by key, or an error if not found or not convertible to float64
RequireFloatSlice returns a float64 slice argument by key, or an error if not found or not convertible to float64 slice
RequireInt returns an int argument by key, or an error if not found or not convertible to int
RequireIntSlice returns an int slice argument by key, or an error if not found or not convertible to int slice
RequireString returns a string argument by key, or an error if not found or not a string
RequireStringSlice returns a string slice argument by key, or an error if not found or not convertible to string slice
func ParseArgument(request CallToolRequest, key string, defaultVal any) any
func ParseBoolean(request CallToolRequest, key string, defaultValue bool) bool
func ParseFloat32(request CallToolRequest, key string, defaultValue float32) float32
func ParseFloat64(request CallToolRequest, key string, defaultValue float64) float64
func ParseInt(request CallToolRequest, key string, defaultValue int) int
func ParseInt16(request CallToolRequest, key string, defaultValue int16) int16
func ParseInt32(request CallToolRequest, key string, defaultValue int32) int32
func ParseInt64(request CallToolRequest, key string, defaultValue int64) int64
func ParseInt8(request CallToolRequest, key string, defaultValue int8) int8
func ParseString(request CallToolRequest, key string, defaultValue string) string
func ParseStringMap(request CallToolRequest, key string, defaultValue map[string]any) map[string]any
func ParseUInt(request CallToolRequest, key string, defaultValue uint) uint
func ParseUInt16(request CallToolRequest, key string, defaultValue uint16) uint16
func ParseUInt32(request CallToolRequest, key string, defaultValue uint32) uint32
func ParseUInt64(request CallToolRequest, key string, defaultValue uint64) uint64
func ParseUInt8(request CallToolRequest, key string, defaultValue uint8) uint8
CallToolResult is the server's response to a tool call.
Any errors that originate from the tool SHOULD be reported inside the result
object, with `isError` set to true, _not_ as an MCP protocol-level error
response. Otherwise, the LLM would not be able to see that an error occurred
and self-correct.
However, any errors in _finding_ the tool, an error indicating that the
server does not support tool calls, or any other exceptional conditions,
should be reported as an MCP error response.
// Can be TextContent, ImageContent, AudioContent, or EmbeddedResource
Whether the tool call ended in an error.
If not set, this is assumed to be false (the call was successful).
Result Result
Result.Meta *Meta
Structured content returned as a JSON object in the structuredContent field of a result.
For backwards compatibility, a tool that returns structured content SHOULD also return
functionally equivalent unstructured content.
MarshalJSON implements custom JSON marshaling for CallToolResult
UnmarshalJSON implements custom JSON unmarshaling for CallToolResult
CallToolResult : github.com/goccy/go-json.Marshaler
*CallToolResult : github.com/goccy/go-json.Unmarshaler
CallToolResult : encoding/json.Marshaler
*CallToolResult : encoding/json.Unmarshaler
func FormatNumberResult(value float64) *CallToolResult
func NewToolResultAudio(text, audioData, mimeType string) *CallToolResult
func NewToolResultError(text string) *CallToolResult
func NewToolResultErrorf(format string, a ...any) *CallToolResult
func NewToolResultErrorFromErr(text string, err error) *CallToolResult
func NewToolResultImage(text, imageData, mimeType string) *CallToolResult
func NewToolResultJSON[T](data T) (*CallToolResult, error)
func NewToolResultResource(text string, resource ResourceContents) *CallToolResult
func NewToolResultStructured(structured any, fallbackText string) *CallToolResult
func NewToolResultStructuredOnly(structured any) *CallToolResult
func NewToolResultText(text string) *CallToolResult
func ParseCallToolResult(rawMessage *json.RawMessage) (*CallToolResult, error)
CancelledNotification can be sent by either side to indicate that it is
cancelling a previously-issued request.
The request SHOULD still be in-flight, but due to communication latency, it
is always possible that this notification MAY arrive after the request has
already finished.
This notification indicates that the result will be unused, so any
associated processing SHOULD cease.
A client MUST NOT attempt to cancel its `initialize` request.
Notification Notification
Notification.Method string
Params CancelledNotificationParams
An optional string describing the reason for the cancellation. This MAY
be logged or presented to the user.
The ID of the request to cancel.
This MUST correspond to the ID of a request previously issued
in the same direction.
CancelTaskRequest cancels an in-progress task.
Header http.Header
Params CancelTaskParams
Request Request
Request.Method string
CancelTaskResult returns the cancelled task state.
Result Result
Result.Meta *Meta
Task Task
ISO 8601 timestamp when the task was created.
ISO 8601 timestamp when the task was last updated.
Suggested time in milliseconds between status checks.
Current state of the task execution.
Optional human-readable message describing the current state.
Time in milliseconds from creation before task may be deleted.
If null, the task has no expiration.
Unique identifier for the task.
GetName returns the task ID, implementing the Named interface for pagination.
CancelTaskResult : Named
func NewCancelTaskResult(task Task) CancelTaskResult
func ParseCancelTaskResult(rawMessage *json.RawMessage) (*CancelTaskResult, error)
ClientCapabilities represents capabilities a client may support. Known
capabilities are defined here, in this schema, but this is not a closed set: any
client can define its own, additional capabilities.
Present if the client supports elicitation requests from the server.
Experimental, non-standard capabilities that the client supports.
Optional, present if the client is advertising extension support.
Present if the client supports listing roots.
Present if the client supports sampling from an LLM.
Present if the client supports task-based execution.
func github.com/mark3labs/mcp-go/server.(*InProcessSession).GetClientCapabilities() ClientCapabilities
func github.com/mark3labs/mcp-go/server.SessionWithClientInfo.GetClientCapabilities() ClientCapabilities
func github.com/mark3labs/mcp-go/server.(*InProcessSession).SetClientCapabilities(clientCapabilities ClientCapabilities)
func github.com/mark3labs/mcp-go/server.SessionWithClientInfo.SetClientCapabilities(clientCapabilities ClientCapabilities)
ClientNotification represents any notification that can be sent from client to server.
ClientRequest represents any request that can be sent from client to server.
ClientResult represents any result that can be sent from client to server.
CompleteArgument is an argument to a completion request
The name of the argument
The value of the argument to use for completion matching.
func github.com/mark3labs/mcp-go/server.(*DefaultPromptCompletionProvider).CompletePromptArgument(ctx context.Context, promptName string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.(*DefaultResourceCompletionProvider).CompleteResourceArgument(ctx context.Context, uri string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.PromptCompletionProvider.CompletePromptArgument(ctx context.Context, promptName string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.ResourceCompletionProvider.CompleteResourceArgument(ctx context.Context, uri string, argument CompleteArgument, context CompleteContext) (*Completion, error)
CompleteContext is the context about already-resolved arguments
Arguments map[string]string
func github.com/mark3labs/mcp-go/server.(*DefaultPromptCompletionProvider).CompletePromptArgument(ctx context.Context, promptName string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.(*DefaultResourceCompletionProvider).CompleteResourceArgument(ctx context.Context, uri string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.PromptCompletionProvider.CompletePromptArgument(ctx context.Context, promptName string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.ResourceCompletionProvider.CompleteResourceArgument(ctx context.Context, uri string, argument CompleteArgument, context CompleteContext) (*Completion, error)
CompleteParams are the parameters for a completion/complete request
Argument CompleteArgument
Context CompleteContext
// Can be PromptReference or ResourceReference
(*CompleteParams) UnmarshalJSON(data []byte) error
*CompleteParams : github.com/goccy/go-json.Unmarshaler
*CompleteParams : encoding/json.Unmarshaler
CompleteRequest is a request from the client to the server, to ask for completion options.
Header http.Header
Params CompleteParams
Request Request
Request.Method string
CompleteResult is the server's response to a completion/complete request
Completion Completion
Result Result
Result.Meta *Meta
Completion is the server's response to a completion/complete request
Indicates whether there are additional completion options beyond those
provided in the current response, even if the exact total is unknown.
The total number of completion options available. This can exceed the
number of values actually sent in the response.
An array of completion values. Must not exceed 100 items.
func github.com/mark3labs/mcp-go/server.(*DefaultPromptCompletionProvider).CompletePromptArgument(ctx context.Context, promptName string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.(*DefaultResourceCompletionProvider).CompleteResourceArgument(ctx context.Context, uri string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.PromptCompletionProvider.CompletePromptArgument(ctx context.Context, promptName string, argument CompleteArgument, context CompleteContext) (*Completion, error)
func github.com/mark3labs/mcp-go/server.ResourceCompletionProvider.CompleteResourceArgument(ctx context.Context, uri string, argument CompleteArgument, context CompleteContext) (*Completion, error)
AudioContent
EmbeddedResource
ImageContent
ResourceLink
TextContent
func ParseContent(contentMap map[string]any) (Content, error)
func UnmarshalContent(data []byte) (Content, error)
func MarshalContent(content Content) ([]byte, error)
func NewPromptMessage(role Role, content Content) PromptMessage
IncludeContext string
MaxTokens int
Messages []SamplingMessage
Metadata any
ModelPreferences *ModelPreferences
StopSequences []string
SystemPrompt string
Temperature float64
CreateMessageRequest is a request from the server to sample an LLM via the
client. The client has full discretion over which model to select. The client
should also inform the user before beginning sampling, to allow them to inspect
the request (human in the loop) and decide whether to approve it.
CreateMessageParams CreateMessageParams
CreateMessageParams.IncludeContext string
CreateMessageParams.MaxTokens int
CreateMessageParams.Messages []SamplingMessage
CreateMessageParams.Metadata any
CreateMessageParams.ModelPreferences *ModelPreferences
CreateMessageParams.StopSequences []string
CreateMessageParams.SystemPrompt string
CreateMessageParams.Temperature float64
Request Request
Request.Method string
Request.Params RequestParams
func github.com/mark3labs/mcp-go/server.(*InProcessSession).RequestSampling(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
func github.com/mark3labs/mcp-go/server.(*MCPServer).RequestSampling(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
func github.com/mark3labs/mcp-go/server.SamplingHandler.CreateMessage(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
func github.com/mark3labs/mcp-go/server.SessionWithSampling.RequestSampling(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
CreateMessageResult is the client's response to a sampling/create_message
request from the server. The client should inform the user before returning the
sampled message, to allow them to inspect the response (human in the loop) and
decide whether to allow the server to see it.
The name of the model that generated the message.
Result Result
Result.Meta *Meta
SamplingMessage SamplingMessage
// Can be TextContent, ImageContent or AudioContent
SamplingMessage.Role Role
The reason why sampling stopped, if known.
func github.com/mark3labs/mcp-go/server.(*InProcessSession).RequestSampling(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
func github.com/mark3labs/mcp-go/server.(*MCPServer).RequestSampling(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
func github.com/mark3labs/mcp-go/server.SamplingHandler.CreateMessage(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
func github.com/mark3labs/mcp-go/server.SessionWithSampling.RequestSampling(ctx context.Context, request CreateMessageRequest) (*CreateMessageResult, error)
CreateTaskResult is returned immediately when a task-augmented request is accepted.
It contains task metadata rather than the actual operation result.
Content []Content
IsError bool
Result Result
Result.Meta *Meta
StructuredContent any
Task Task
func NewCreateTaskResult(task Task) CreateTaskResult
Cursor is an opaque token used to represent a cursor for pagination.
func NewListPromptsResult(prompts []Prompt, nextCursor Cursor) *ListPromptsResult
func NewListResourcesResult(resources []Resource, nextCursor Cursor) *ListResourcesResult
func NewListResourceTemplatesResult(templates []ResourceTemplate, nextCursor Cursor) *ListResourceTemplatesResult
func NewListToolsResult(tools []Tool, nextCursor Cursor) *ListToolsResult
ElicitationCapability represents the elicitation capabilities of a client or server.
// Supports form mode
// Supports URL mode
ElicitationParams contains the parameters for an elicitation request.
ElicitationID is a unique identifier for the elicitation request.
A human-readable message explaining what information is being requested and why.
Meta *Meta
Mode specifies the type of elicitation: "form" or "url". Defaults to "form".
A JSON Schema defining the expected structure of the user's response.
URL is the URL to be opened by the user.
Validate checks if the elicitation parameters are valid.
ElicitationRequest is a request from the server to the client to request additional
information from the user during an interaction.
Params ElicitationParams
Request Request
Request.Method string
func github.com/mark3labs/mcp-go/server.ElicitationHandler.Elicit(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
func github.com/mark3labs/mcp-go/server.(*InProcessSession).RequestElicitation(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
func github.com/mark3labs/mcp-go/server.(*MCPServer).RequestElicitation(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
func github.com/mark3labs/mcp-go/server.SessionWithElicitation.RequestElicitation(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
ElicitationResponse represents the user's response to an elicitation request.
Action indicates whether the user accepted, declined, or cancelled.
Content contains the user's response data if they accepted.
Should conform to the requestedSchema from the ElicitationRequest.
ElicitationResponseAction indicates how the user responded to an elicitation request.
const ElicitationResponseActionAccept
const ElicitationResponseActionCancel
const ElicitationResponseActionDecline
ElicitationResult represents the result of an elicitation request.
ElicitationResponse ElicitationResponse
Action indicates whether the user accepted, declined, or cancelled.
Content contains the user's response data if they accepted.
Should conform to the requestedSchema from the ElicitationRequest.
Result Result
Result.Meta *Meta
func github.com/mark3labs/mcp-go/server.ElicitationHandler.Elicit(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
func github.com/mark3labs/mcp-go/server.(*InProcessSession).RequestElicitation(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
func github.com/mark3labs/mcp-go/server.(*MCPServer).RequestElicitation(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
func github.com/mark3labs/mcp-go/server.(*MCPServer).RequestURLElicitation(ctx context.Context, session server.ClientSession, elicitationID string, url string, message string) (*ElicitationResult, error)
func github.com/mark3labs/mcp-go/server.SessionWithElicitation.RequestElicitation(ctx context.Context, request ElicitationRequest) (*ElicitationResult, error)
EmbeddedResource represents the contents of a resource, embedded into a prompt or tool call result.
It is up to the client how best to render embedded resources for the
benefit of the LLM and/or the user.
Annotated Annotated
Annotated.Annotations *Annotations
Meta is a metadata object that is reserved by MCP for storing additional information.
Resource ResourceContents
Type string
EmbeddedResource : Content
func AsEmbeddedResource(content any) (*EmbeddedResource, bool)
func NewEmbeddedResource(resource ResourceContents) EmbeddedResource
Arguments to use for templating the prompt.
The name of the prompt or prompt template.
GetPromptRequest is used by the client to get a prompt provided by the
server.
Header http.Header
Params GetPromptParams
Request Request
Request.Method string
GetPromptResult is the server's response to a prompts/get request from the
client.
An optional description for the prompt.
Messages []PromptMessage
Result Result
Result.Meta *Meta
func NewGetPromptResult(description string, messages []PromptMessage) *GetPromptResult
func ParseGetPromptResult(rawMessage *json.RawMessage) (*GetPromptResult, error)
GetTaskRequest retrieves the current status of a task.
Header http.Header
Params GetTaskParams
Request Request
Request.Method string
GetTaskResult returns the current state of a task.
Result Result
Result.Meta *Meta
Task Task
ISO 8601 timestamp when the task was created.
ISO 8601 timestamp when the task was last updated.
Suggested time in milliseconds between status checks.
Current state of the task execution.
Optional human-readable message describing the current state.
Time in milliseconds from creation before task may be deleted.
If null, the task has no expiration.
Unique identifier for the task.
GetName returns the task ID, implementing the Named interface for pagination.
GetTaskResult : Named
func NewGetTaskResult(task Task) GetTaskResult
func ParseGetTaskResult(rawMessage *json.RawMessage) (*GetTaskResult, error)
Icon represents a visual identifier for MCP entities.
Security considerations:
- Clients MUST support at least image/png and image/jpeg MIME types
- Clients SHOULD support image/svg+xml and image/webp
- Icons should be treated as untrusted input
- URI scheme validation (HTTPS or data URI only)
- Size/dimension limits to prevent resource exhaustion
Optional MIME type (e.g., "image/png", "image/svg+xml")
Optional size specifications (e.g., ["48x48"], ["any"] for SVG)
URI pointing to the icon resource (HTTPS URL or data URI)
func WithPromptIcons(icons ...Icon) PromptOption
func WithResourceIcons(icons ...Icon) ResourceOption
func WithTemplateIcons(icons ...Icon) ResourceTemplateOption
func WithToolIcons(icons ...Icon) ToolOption
func github.com/mark3labs/mcp-go/server.WithIcons(icons ...Icon) server.ServerOption
ImageContent represents an image provided to or from an LLM.
It must have Type set to "image".
Annotated Annotated
Annotated.Annotations *Annotations
The base64-encoded image data.
The MIME type of the image. Different providers may support different image types.
Meta is a metadata object that is reserved by MCP for storing additional information.
// Must be "image"
ImageContent : Content
func AsImageContent(content any) (*ImageContent, bool)
func NewImageContent(data, mimeType string) ImageContent
Implementation describes the name and version of an MCP implementation.
Description string
Icons provides visual identifiers for the implementation
Name string
Title string
Version string
WebsiteURL string
func github.com/mark3labs/mcp-go/server.(*InProcessSession).GetClientInfo() Implementation
func github.com/mark3labs/mcp-go/server.SessionWithClientInfo.GetClientInfo() Implementation
func NewInitializeResult(protocolVersion string, capabilities ServerCapabilities, serverInfo Implementation, instructions string) *InitializeResult
func github.com/mark3labs/mcp-go/server.(*InProcessSession).SetClientInfo(clientInfo Implementation)
func github.com/mark3labs/mcp-go/server.SessionWithClientInfo.SetClientInfo(clientInfo Implementation)
InitializedNotification is sent from the client to the server after
initialization has finished.
Notification Notification
Notification.Method string
Notification.Params NotificationParams
Capabilities ClientCapabilities
ClientInfo Implementation
The latest version of the Model Context Protocol that the client supports.
The client MAY decide to support older versions as well.
InitializeRequest is sent from the client to the server when it first
connects, asking it to begin initialization.
Header http.Header
Params InitializeParams
Request Request
Request.Method string
InitializeResult is sent after receiving an initialize request from the
client.
Capabilities ServerCapabilities
Instructions describing how to use the server and its features.
This can be used by clients to improve the LLM's understanding of
available tools, resources, etc. It can be thought of like a "hint" to the model.
For example, this information MAY be added to the system prompt.
The version of the Model Context Protocol that the server wants to use.
This may not match the version that the client requested. If the client cannot
support this version, it MUST disconnect.
Result Result
Result.Meta *Meta
ServerInfo Implementation
func NewInitializeResult(protocolVersion string, capabilities ServerCapabilities, serverInfo Implementation, instructions string) *InitializeResult
JSONRPCError represents a non-successful (error) response to a request.
Error JSONRPCErrorDetails
ID RequestId
JSONRPC string
func NewJSONRPCError(id RequestId, code int, message string, data any) JSONRPCError
func URLElicitationRequiredError.JSONRPCError() JSONRPCError
JSONRPCErrorDetails represents a JSON-RPC error for Go error handling.
This is separate from the JSONRPCError type which represents the full JSON-RPC error response structure.
The error type that occurred.
Additional information about the error. The value of this member
is defined by the sender (e.g. detailed error information, nested errors etc.).
A short description of the error. The message SHOULD be limited
to a concise single sentence.
AsError maps JSONRPCErrorDetails to a Go error.
Returns sentinel errors wrapped with custom messages for known codes.
Defaults to a generic error with the original message when the code is not mapped.
func NewJSONRPCErrorDetails(code int, message string, data any) JSONRPCErrorDetails
JSONRPCMessage represents either a JSONRPCRequest, JSONRPCNotification, JSONRPCResponse, or JSONRPCError
func github.com/mark3labs/mcp-go/server.(*MCPServer).HandleMessage(ctx context.Context, message json.RawMessage) JSONRPCMessage
JSONRPCNotification represents a notification which does not expect a response.
JSONRPC string
Notification Notification
Notification.Method string
Notification.Params NotificationParams
func NewElicitationCompleteNotification(elicitationID string) JSONRPCNotification
func github.com/mark3labs/mcp-go/server.ClientSession.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.(*InProcessSession).NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithClientInfo.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithElicitation.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithLogging.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithResources.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithResourceTemplates.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithRoots.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithSampling.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithStreamableHTTPConfig.NotificationChannel() chan<- JSONRPCNotification
func github.com/mark3labs/mcp-go/server.SessionWithTools.NotificationChannel() chan<- JSONRPCNotification
JSONRPCRequest represents a request that expects a response.
ID RequestId
JSONRPC string
Params any
Request Request
Request.Method string
JSONRPCResponse represents a successful (non-error) response to a request.
ID RequestId
JSONRPC string
Result any
func NewJSONRPCResponse(id RequestId, result Result) JSONRPCResponse
func NewJSONRPCResultResponse(id RequestId, result any) JSONRPCResponse
ListPromptsRequest is sent from the client to request a list of prompts and
prompt templates the server has.
Header http.Header
PaginatedRequest PaginatedRequest
PaginatedRequest.Params PaginatedParams
PaginatedRequest.Request Request
PaginatedRequest.Request.Method string
ListPromptsResult is the server's response to a prompts/list request from
the client.
PaginatedResult PaginatedResult
An opaque token representing the pagination position after the last
returned result.
If present, there may be more results available.
PaginatedResult.Result Result
PaginatedResult.Result.Meta *Meta
Prompts []Prompt
func NewListPromptsResult(prompts []Prompt, nextCursor Cursor) *ListPromptsResult
ListResourcesRequest is sent from the client to request a list of resources
the server has.
Header http.Header
PaginatedRequest PaginatedRequest
PaginatedRequest.Params PaginatedParams
PaginatedRequest.Request Request
PaginatedRequest.Request.Method string
ListResourcesResult is the server's response to a resources/list request
from the client.
PaginatedResult PaginatedResult
An opaque token representing the pagination position after the last
returned result.
If present, there may be more results available.
PaginatedResult.Result Result
PaginatedResult.Result.Meta *Meta
Resources []Resource
func NewListResourcesResult(resources []Resource, nextCursor Cursor) *ListResourcesResult
ListResourceTemplatesRequest is sent from the client to request a list of
resource templates the server has.
Header http.Header
PaginatedRequest PaginatedRequest
PaginatedRequest.Params PaginatedParams
PaginatedRequest.Request Request
PaginatedRequest.Request.Method string
ListResourceTemplatesResult is the server's response to a
resources/templates/list request from the client.
PaginatedResult PaginatedResult
An opaque token representing the pagination position after the last
returned result.
If present, there may be more results available.
PaginatedResult.Result Result
PaginatedResult.Result.Meta *Meta
ResourceTemplates []ResourceTemplate
func NewListResourceTemplatesResult(templates []ResourceTemplate, nextCursor Cursor) *ListResourceTemplatesResult
ListRootsRequest is sent from the server to request a list of root URIs from the client. Roots allow
servers to ask for specific directories or files to operate on. A common example
for roots is providing a set of repositories or directories a server should operate
on.
This request is typically used when the server needs to understand the file system
structure or access specific locations that the client has permission to read from.
Request Request
Request.Method string
Request.Params RequestParams
func github.com/mark3labs/mcp-go/server.(*InProcessSession).ListRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
func github.com/mark3labs/mcp-go/server.(*MCPServer).RequestRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
func github.com/mark3labs/mcp-go/server.RootsHandler.ListRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
func github.com/mark3labs/mcp-go/server.SessionWithRoots.ListRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
ListRootsResult is the client's response to a roots/list request from the server.
This result contains an array of Root objects, each representing a root directory
or file that the server can operate on.
Result Result
Result.Meta *Meta
Roots []Root
func github.com/mark3labs/mcp-go/server.(*InProcessSession).ListRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
func github.com/mark3labs/mcp-go/server.(*MCPServer).RequestRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
func github.com/mark3labs/mcp-go/server.RootsHandler.ListRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
func github.com/mark3labs/mcp-go/server.SessionWithRoots.ListRoots(ctx context.Context, request ListRootsRequest) (*ListRootsResult, error)
ListTasksRequest retrieves a paginated list of tasks.
Header http.Header
PaginatedRequest PaginatedRequest
PaginatedRequest.Params PaginatedParams
PaginatedRequest.Request Request
PaginatedRequest.Request.Method string
ListTasksResult returns a list of tasks.
PaginatedResult PaginatedResult
An opaque token representing the pagination position after the last
returned result.
If present, there may be more results available.
PaginatedResult.Result Result
PaginatedResult.Result.Meta *Meta
Tasks []Task
func NewListTasksResult(tasks []Task) ListTasksResult
func ParseListTasksResult(rawMessage *json.RawMessage) (*ListTasksResult, error)
ListToolsRequest is sent from the client to request a list of tools the
server has.
Header http.Header
PaginatedRequest PaginatedRequest
PaginatedRequest.Params PaginatedParams
PaginatedRequest.Request Request
PaginatedRequest.Request.Method string
ListToolsResult is the server's response to a tools/list request from the
client.
PaginatedResult PaginatedResult
An opaque token representing the pagination position after the last
returned result.
If present, there may be more results available.
PaginatedResult.Result Result
PaginatedResult.Result.Meta *Meta
Tools []Tool
func NewListToolsResult(tools []Tool, nextCursor Cursor) *ListToolsResult
LoggingLevel represents the severity of a log message.
These map to syslog message severities, as specified in RFC-5424:
https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1
( LoggingLevel) ShouldSendTo(minLevel LoggingLevel) bool
func github.com/mark3labs/mcp-go/server.(*InProcessSession).GetLogLevel() LoggingLevel
func github.com/mark3labs/mcp-go/server.SessionWithLogging.GetLogLevel() LoggingLevel
func NewLoggingMessageNotification(level LoggingLevel, logger string, data any) LoggingMessageNotification
func LoggingLevel.ShouldSendTo(minLevel LoggingLevel) bool
func github.com/mark3labs/mcp-go/server.(*InProcessSession).SetLogLevel(level LoggingLevel)
func github.com/mark3labs/mcp-go/server.SessionWithLogging.SetLogLevel(level LoggingLevel)
const LoggingLevelAlert
const LoggingLevelCritical
const LoggingLevelDebug
const LoggingLevelEmergency
const LoggingLevelError
const LoggingLevelInfo
const LoggingLevelNotice
const LoggingLevelWarning
LoggingMessageNotification is a notification of a log message passed from
server to client. If no logging/setLevel request has been sent from the client,
the server MAY decide which messages to send automatically.
Notification Notification
Notification.Method string
Params LoggingMessageNotificationParams
func NewLoggingMessageNotification(level LoggingLevel, logger string, data any) LoggingMessageNotification
func github.com/mark3labs/mcp-go/server.(*MCPServer).SendLogMessageToClient(ctx context.Context, notification LoggingMessageNotification) error
func github.com/mark3labs/mcp-go/server.(*MCPServer).SendLogMessageToSpecificClient(sessionID string, notification LoggingMessageNotification) error
The data to be logged, such as a string message or an object. Any JSON
serializable type is allowed here.
The severity of this log message.
An optional name of the logger issuing this message.
func github.com/mark3labs/mcp-go/server.(*UnparsableMessageError).GetMethod() MCPMethod
const MethodCompletionComplete
const MethodElicitationCreate
const MethodInitialize
const MethodListRoots
const MethodNotificationElicitationComplete
const MethodPing
const MethodPromptsGet
const MethodPromptsList
const MethodResourcesList
const MethodResourcesRead
const MethodResourcesTemplatesList
const MethodSamplingCreateMessage
const MethodSetLogLevel
const MethodTasksCancel
const MethodTasksGet
const MethodTasksList
const MethodTasksResult
const MethodToolsCall
const MethodToolsList
Meta is metadata attached to a request's parameters. This can include fields
formally defined by the protocol or other arbitrary data.
AdditionalFields are any fields present in the Meta that are not
otherwise defined in the protocol.
If specified, the caller is requesting out-of-band progress
notifications for this request (as represented by
notifications/progress). The value of this parameter is an
opaque token that will be attached to any subsequent
notifications. The receiver is not obligated to provide these
notifications.
(*Meta) MarshalJSON() ([]byte, error)
(*Meta) UnmarshalJSON(data []byte) error
*Meta : github.com/goccy/go-json.Marshaler
*Meta : github.com/goccy/go-json.Unmarshaler
*Meta : encoding/json.Marshaler
*Meta : encoding/json.Unmarshaler
func NewMetaFromMap(m map[string]any) *Meta
func WithModelImmediateResponse(message string) *Meta
func WithRelatedTask(taskID string) *Meta
ModelHint represents hints to use for model selection.
Keys not declared here are currently left unspecified by the spec and are up
to the client to interpret.
A hint for a model name.
The client SHOULD treat this as a substring of a model name; for example:
- `claude-3-5-sonnet` should match `claude-3-5-sonnet-20241022`
- `sonnet` should match `claude-3-5-sonnet-20241022`, `claude-3-sonnet-20240229`, etc.
- `claude` should match any Claude model
The client MAY also map the string to a different provider's model name or
a different model family, as long as it fills a similar niche; for example:
- `gemini-1.5-flash` could match `claude-3-haiku-20240307`
ModelPreferences represents the server's preferences for model selection,
requested of the client during sampling.
Because LLMs can vary along multiple dimensions, choosing the "best" modelis
rarely straightforward. Different models excel in different areas—some are
faster but less capable, others are more capable but more expensive, and so
on. This interface allows servers to express their priorities across multiple
dimensions to help clients make an appropriate selection for their use case.
These preferences are always advisory. The client MAY ignore them. It is also
up to the client to decide how to interpret these preferences and how to
balance them against other considerations.
How much to prioritize cost when selecting a model. A value of 0 means cost
is not important, while a value of 1 means cost is the most important
factor.
Optional hints to use for model selection.
If multiple hints are specified, the client MUST evaluate them in order
(such that the first match is taken).
The client SHOULD prioritize these hints over the numeric priorities, but
MAY still use the priorities to select from ambiguous matches.
How much to prioritize intelligence and capabilities when selecting a
model. A value of 0 means intelligence is not important, while a value of 1
means intelligence is the most important factor.
How much to prioritize sampling speed (latency) when selecting a model. A
value of 0 means speed is not important, while a value of 1 means speed is
the most important factor.
( Named) GetName() string
CancelTaskResult
GetTaskResult
Prompt
Resource
ResourceTemplate
Task
TaskStatusNotificationParams
Tool
*github.com/apache/arrow-go/v18/parquet/internal/gen-go/parquet.SchemaElement
*github.com/polarsignals/frostdb/gen/proto/go/frostdb/schema/v1alpha1.Column
*github.com/polarsignals/frostdb/gen/proto/go/frostdb/schema/v1alpha1.Schema
*github.com/polarsignals/frostdb/gen/proto/go/frostdb/schema/v1alpha1.SortingColumn
*github.com/polarsignals/frostdb/gen/proto/go/frostdb/schema/v1alpha2.Group
*github.com/polarsignals/frostdb/gen/proto/go/frostdb/schema/v1alpha2.Leaf
*github.com/polarsignals/frostdb/gen/proto/go/frostdb/snapshot/v1alpha1.Table
*github.com/prometheus/client_model/go.LabelPair
*github.com/prometheus/client_model/go.MetricFamily
*go.opentelemetry.io/proto/otlp/common/v1.InstrumentationScope
*go.opentelemetry.io/proto/otlp/trace/v1.Span
*go.opentelemetry.io/proto/otlp/trace/v1.Span_Event
*google.golang.org/protobuf/types/descriptorpb.DescriptorProto
*google.golang.org/protobuf/types/descriptorpb.EnumDescriptorProto
*google.golang.org/protobuf/types/descriptorpb.EnumValueDescriptorProto
*google.golang.org/protobuf/types/descriptorpb.FieldDescriptorProto
*google.golang.org/protobuf/types/descriptorpb.FileDescriptorProto
*google.golang.org/protobuf/types/descriptorpb.MethodDescriptorProto
*google.golang.org/protobuf/types/descriptorpb.OneofDescriptorProto
*google.golang.org/protobuf/types/descriptorpb.ServiceDescriptorProto
*gorm.io/gorm/schema.CheckConstraint
*gorm.io/gorm/schema.Constraint
gorm.io/gorm/schema.ConstraintInterface (interface)
*gorm.io/gorm/schema.UniqueConstraint
Additional fields can be added to this map
This parameter name is reserved by MCP to allow clients and
servers to attach additional metadata to their notifications.
MarshalJSON implements custom JSON marshaling
UnmarshalJSON implements custom JSON unmarshaling
NotificationParams : github.com/goccy/go-json.Marshaler
*NotificationParams : github.com/goccy/go-json.Unmarshaler
NotificationParams : encoding/json.Marshaler
*NotificationParams : encoding/json.Unmarshaler
An opaque token representing the current pagination position.
If provided, the server should return results starting after this cursor.
An opaque token representing the pagination position after the last
returned result.
If present, there may be more results available.
Result Result
Result.Meta *Meta
type Params (map)
PingRequest represents a ping, issued by either the server or the client,
to check that the other party is still alive. The receiver must promptly respond,
or else may be disconnected.
Header http.Header
Request Request
Request.Method string
Request.Params RequestParams
ProgressNotification is an out-of-band notification used to inform the
receiver of a progress update for a long-running request.
Notification Notification
Notification.Method string
Params ProgressNotificationParams
func NewProgressNotification(token ProgressToken, progress float64, total *float64, message *string) ProgressNotification
Message related to progress. This should provide relevant human-readable
progress information.
The progress thus far. This should increase every time progress is made,
even if the total is unknown.
The progress token which was given in the initial request, used to
associate this notification with the request that is proceeding.
Total number of items to process (or total progress required), if known.
ProgressToken is used to associate progress notifications with the original request.
func NewProgressNotification(token ProgressToken, progress float64, total *float64, message *string) ProgressNotification
Prompt represents a prompt or prompt template that the server offers.
If Arguments is non-nil and non-empty, this indicates the prompt is a template
that requires argument values to be provided when calling prompts/get.
If Arguments is nil or empty, this is a static prompt that takes no arguments.
A list of arguments to use for templating the prompt.
The presence of arguments indicates this is a template prompt.
An optional description of what this prompt provides
Icons provides visual identifiers for the prompt
Meta is a metadata object that is reserved by MCP for storing additional information.
The name of the prompt or prompt template.
GetName returns the name of the prompt.
Prompt : Named
func NewPrompt(name string, opts ...PromptOption) Prompt
func NewListPromptsResult(prompts []Prompt, nextCursor Cursor) *ListPromptsResult
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddPrompt(prompt Prompt, handler server.PromptHandlerFunc)
PromptArgument describes an argument that a prompt template can accept.
When a prompt includes arguments, clients must provide values for all
required arguments when making a prompts/get request.
A human-readable description of the argument.
The name of the argument.
Whether this argument must be provided.
If true, clients must include this argument when calling prompts/get.
PromptListChangedNotification is an optional notification from the server
to the client, informing it that the list of prompts it offers has changed. This
may be issued by servers without any previous subscription from the client.
Notification Notification
Notification.Method string
Notification.Params NotificationParams
PromptMessage describes a message returned as part of a prompt.
This is similar to `SamplingMessage`, but also supports the embedding of
resources from the MCP server.
// Can be TextContent, ImageContent, AudioContent or EmbeddedResource
Role Role
func NewPromptMessage(role Role, content Content) PromptMessage
func NewGetPromptResult(description string, messages []PromptMessage) *GetPromptResult
PromptOption is a function that configures a Prompt.
It provides a flexible way to set various properties of a Prompt using the functional options pattern.
func WithArgument(name string, opts ...ArgumentOption) PromptOption
func WithPromptDescription(description string) PromptOption
func WithPromptIcons(icons ...Icon) PromptOption
func NewPrompt(name string, opts ...PromptOption) Prompt
PropertyOption is a function that configures a property in a Tool's input schema.
It allows for flexible configuration of JSON Schema properties using the functional options pattern.
func AdditionalProperties(schema any) PropertyOption
func DefaultArray[T](value []T) PropertyOption
func DefaultBool(value bool) PropertyOption
func DefaultNumber(value float64) PropertyOption
func DefaultString(value string) PropertyOption
func Description(desc string) PropertyOption
func Enum(values ...string) PropertyOption
func Items(schema any) PropertyOption
func Max(max float64) PropertyOption
func MaxItems(max int) PropertyOption
func MaxLength(max int) PropertyOption
func MaxProperties(max int) PropertyOption
func Min(min float64) PropertyOption
func MinItems(min int) PropertyOption
func MinLength(min int) PropertyOption
func MinProperties(min int) PropertyOption
func MultipleOf(value float64) PropertyOption
func Pattern(pattern string) PropertyOption
func Properties(props map[string]any) PropertyOption
func PropertyNames(schema map[string]any) PropertyOption
func Required() PropertyOption
func Title(title string) PropertyOption
func UniqueItems(unique bool) PropertyOption
func WithBooleanItems(opts ...PropertyOption) PropertyOption
func WithNumberItems(opts ...PropertyOption) PropertyOption
func WithStringEnumItems(values []string) PropertyOption
func WithStringItems(opts ...PropertyOption) PropertyOption
func WithAny(name string, opts ...PropertyOption) ToolOption
func WithArray(name string, opts ...PropertyOption) ToolOption
func WithBoolean(name string, opts ...PropertyOption) ToolOption
func WithBooleanItems(opts ...PropertyOption) PropertyOption
func WithNumber(name string, opts ...PropertyOption) ToolOption
func WithNumberItems(opts ...PropertyOption) PropertyOption
func WithObject(name string, opts ...PropertyOption) ToolOption
func WithString(name string, opts ...PropertyOption) ToolOption
func WithStringItems(opts ...PropertyOption) PropertyOption
Arguments to pass to the resource handler
The URI of the resource to read. The URI can use any protocol; it is up
to the server how to interpret it.
ReadResourceRequest is sent from the client to the server, to read a
specific resource URI.
Header http.Header
Params ReadResourceParams
Request Request
Request.Method string
ReadResourceResult is the server's response to a resources/read request
from the client.
// Can be TextResourceContents or BlobResourceContents
Result Result
Result.Meta *Meta
func NewReadResourceResult(text string) *ReadResourceResult
func ParseReadResourceResult(rawMessage *json.RawMessage) (*ReadResourceResult, error)
RequestId is a uniquely identifying ID for a request in JSON-RPC.
It can be any JSON-serializable value, typically a number or string.
IsNil returns true if the RequestId is nil
( RequestId) MarshalJSON() ([]byte, error)
String returns a string representation of the RequestId
(*RequestId) UnmarshalJSON(data []byte) error
Value returns the underlying value of the RequestId
RequestId : github.com/goccy/go-json.Marshaler
*RequestId : github.com/goccy/go-json.Unmarshaler
RequestId : encoding/json.Marshaler
*RequestId : encoding/json.Unmarshaler
RequestId : expvar.Var
RequestId : fmt.Stringer
func NewRequestId(value any) RequestId
func NewJSONRPCError(id RequestId, code int, message string, data any) JSONRPCError
func NewJSONRPCResponse(id RequestId, result Result) JSONRPCResponse
func NewJSONRPCResultResponse(id RequestId, result any) JSONRPCResponse
Resource represents a known resource that the server is capable of reading.
Annotated Annotated
Annotated.Annotations *Annotations
A description of what this resource represents.
This can be used by clients to improve the LLM's understanding of
available resources. It can be thought of like a "hint" to the model.
Icons provides visual identifiers for the resource
The MIME type of this resource, if known.
Meta is a metadata object that is reserved by MCP for storing additional information.
A human-readable name for this resource.
This can be used by clients to populate UI elements.
The URI of this resource.
GetName returns the name of the resource.
Resource : Named
func NewResource(uri string, name string, opts ...ResourceOption) Resource
func NewListResourcesResult(resources []Resource, nextCursor Cursor) *ListResourcesResult
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddResource(resource Resource, handler server.ResourceHandlerFunc)
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddSessionResource(sessionID string, resource Resource, handler server.ResourceHandlerFunc) error
ResourceContents represents the contents of a specific resource or sub-
resource.
BlobResourceContents
TextResourceContents
func ParseResourceContents(contentMap map[string]any) (ResourceContents, error)
func NewEmbeddedResource(resource ResourceContents) EmbeddedResource
func NewToolResultResource(text string, resource ResourceContents) *CallToolResult
ResourceLink represents a link to a resource that the client can access.
Annotated Annotated
Annotated.Annotations *Annotations
The description of the resource.
The MIME type of the resource.
The name of the resource.
// Must be "resource_link"
The URI of the resource.
ResourceLink : Content
func NewResourceLink(uri, name, description, mimeType string) ResourceLink
ResourceListChangedNotification is an optional notification from the server
to the client, informing it that the list of resources it can read from has
changed. This may be issued by servers without any previous subscription from
the client.
Notification Notification
Notification.Method string
Notification.Params NotificationParams
ResourceOption is a function that configures a Resource.
It provides a flexible way to set various properties of a Resource using the functional options pattern.
func WithAnnotations(audience []Role, priority float64, lastModified string) ResourceOption
func WithLastModified(timestamp string) ResourceOption
func WithMIMEType(mimeType string) ResourceOption
func WithResourceDescription(description string) ResourceOption
func WithResourceIcons(icons ...Icon) ResourceOption
func NewResource(uri string, name string, opts ...ResourceOption) Resource
ResourceReference is a reference to a resource or resource template definition.
Type string
The URI or URI template of the resource.
ResourceTemplate represents a template description for resources available
on the server.
Annotated Annotated
Annotated.Annotations *Annotations
A description of what this template is for.
This can be used by clients to improve the LLM's understanding of
available resources. It can be thought of like a "hint" to the model.
Icons provides visual identifiers for the resource template
The MIME type for all resources that match this template. This should only
be included if all resources matching this template have the same type.
Meta is a metadata object that is reserved by MCP for storing additional information.
A human-readable name for the type of resource this template refers to.
This can be used by clients to populate UI elements.
A URI template (according to RFC 6570) that can be used to construct
resource URIs.
GetName returns the name of the resourceTemplate.
ResourceTemplate : Named
func NewResourceTemplate(uriTemplate string, name string, opts ...ResourceTemplateOption) ResourceTemplate
func NewListResourceTemplatesResult(templates []ResourceTemplate, nextCursor Cursor) *ListResourceTemplatesResult
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddResourceTemplate(template ResourceTemplate, handler server.ResourceTemplateHandlerFunc)
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddSessionResourceTemplate(sessionID string, template ResourceTemplate, handler server.ResourceTemplateHandlerFunc) error
ResourceTemplateOption is a function that configures a ResourceTemplate.
It provides a flexible way to set various properties of a ResourceTemplate using the functional options pattern.
func WithTemplateAnnotations(audience []Role, priority float64, lastModified string) ResourceTemplateOption
func WithTemplateDescription(description string) ResourceTemplateOption
func WithTemplateIcons(icons ...Icon) ResourceTemplateOption
func WithTemplateMIMEType(mimeType string) ResourceTemplateOption
func NewResourceTemplate(uriTemplate string, name string, opts ...ResourceTemplateOption) ResourceTemplate
ResourceUpdatedNotification is a notification from the server to the client,
informing it that a resource has changed and may need to be read again. This
should only be sent if the client previously sent a resources/subscribe request.
Notification Notification
Notification.Method string
Params ResourceUpdatedNotificationParams
The URI of the resource to subscribe to. The URI can use any protocol; it
is up to the server how to interpret it.
Meta *Meta
func NewJSONRPCResponse(id RequestId, result Result) JSONRPCResponse
Role represents the sender or recipient of messages and data in a
conversation.
func NewPromptMessage(role Role, content Content) PromptMessage
func WithAnnotations(audience []Role, priority float64, lastModified string) ResourceOption
func WithTemplateAnnotations(audience []Role, priority float64, lastModified string) ResourceTemplateOption
const RoleAssistant
const RoleUser
Root represents a root directory or file that the server can operate on.
Meta is a metadata object that is reserved by MCP for storing additional information.
An optional name for the root. This can be used to provide a human-readable
identifier for the root, which may be useful for display purposes or for
referencing the root in other parts of the application.
The URI identifying the root. This *must* start with file:// for now.
This restriction may be relaxed in future versions of the protocol to allow
other URI schemes.
RootsListChangedNotification is a notification from the client to the
server, informing it that the list of roots has changed.
This notification should be sent whenever the client adds, removes, or modifies any root.
The server should then request an updated list of roots using the ListRootsRequest.
Notification Notification
Notification.Method string
Notification.Params NotificationParams
SamplingMessage describes a message issued to or received from an LLM API.
// Can be TextContent, ImageContent or AudioContent
Role Role
ServerCapabilities represents capabilities that a server may support. Known
capabilities are defined here, in this schema, but this is not a closed set: any
server can define its own, additional capabilities.
Present if the server supports completions requests to the client.
Present if the server supports elicitation requests to the client.
Experimental, non-standard capabilities that the server supports.
Optional, present if the server is advertising extension support.
Present if the server supports sending log messages to the client.
Present if the server offers any prompt templates.
Present if the server offers any resources to read.
Present if the server supports roots requests to the client.
Present if the server supports sending sampling requests to clients.
Present if the server supports task-based execution.
Present if the server offers any tools to call.
func NewInitializeResult(protocolVersion string, capabilities ServerCapabilities, serverInfo Implementation, instructions string) *InitializeResult
ServerNotification represents any notification that can be sent from server to client.
ServerRequest represents any request that can be sent from server to client.
ServerResult represents any result that can be sent from server to client.
The level of logging that the client wants to receive from the server.
The server should send all logs at this level and higher (i.e., more severe) to
the client as notifications/logging/message.
SetLevelRequest is a request from the client to the server, to enable or
adjust logging.
Header http.Header
Params SetLevelParams
Request Request
Request.Method string
Type Parameters:
TArgs: any
TResult: any
StructuredToolHandlerFunc is a function that handles a tool call with typed arguments and returns structured output
func NewStructuredToolHandler[TArgs, TResult](handler StructuredToolHandlerFunc[TArgs, TResult]) func(ctx context.Context, request CallToolRequest) (*CallToolResult, error)
The URI of the resource to subscribe to. The URI can use any protocol; it
is up to the server how to interpret it.
SubscribeRequest is sent from the client to request resources/updated
notifications from the server whenever a particular resource changes.
Header http.Header
Params SubscribeParams
Request Request
Request.Method string
Task represents the execution state of a request.
ISO 8601 timestamp when the task was created.
ISO 8601 timestamp when the task was last updated.
Suggested time in milliseconds between status checks.
Current state of the task execution.
Optional human-readable message describing the current state.
Time in milliseconds from creation before task may be deleted.
If null, the task has no expiration.
Unique identifier for the task.
GetName returns the task ID, implementing the Named interface for pagination.
Task : Named
func NewTask(taskId string, opts ...TaskOption) Task
func NewCancelTaskResult(task Task) CancelTaskResult
func NewCreateTaskResult(task Task) CreateTaskResult
func NewGetTaskResult(task Task) GetTaskResult
func NewListTasksResult(tasks []Task) ListTasksResult
func NewTaskStatusNotification(task Task) TaskStatusNotification
TaskOption is a function that configures a Task.
It provides a flexible way to set various properties of a Task using the functional options pattern.
func WithTaskCreatedAt(createdAt string) TaskOption
func WithTaskPollInterval(intervalMs int64) TaskOption
func WithTaskStatus(status TaskStatus) TaskOption
func WithTaskStatusMessage(message string) TaskOption
func WithTaskTTL(ttlMs int64) TaskOption
func NewTask(taskId string, opts ...TaskOption) Task
TaskParams represents the task metadata included when augmenting a request.
Requested duration in milliseconds to retain task from creation.
func NewTaskParams(ttlMs *int64) TaskParams
TaskRequestsCapability indicates which request types support task augmentation.
Elicitation-related capabilities.
Sampling-related capabilities.
Tool-related capabilities.
TaskResultRequest retrieves the result of a completed task.
Header http.Header
Params TaskResultParams
Request Request
Request.Method string
TaskResultResult contains the actual operation result.
For task-augmented tool calls, this embeds the CallToolResult fields.
Tool call result fields (for task-augmented tool calls)
IsError bool
Result Result
Result.Meta *Meta
StructuredContent any
func ParseTaskResultResult(rawMessage *json.RawMessage) (*TaskResultResult, error)
TasksCapability represents the task capabilities that a client or server may support.
Tasks enable long-running, asynchronous operations with status polling.
Whether the party supports the tasks/cancel operation.
Whether the party supports the tasks/list operation.
Requests that can be augmented with task metadata.
func NewTasksCapability() *TasksCapability
func NewTasksCapabilityWithToolsOnly() *TasksCapability
TaskStatus represents the execution state of a task.
IsTerminal returns true if the task status is terminal (completed, failed, or cancelled).
func WithTaskStatus(status TaskStatus) TaskOption
const TaskStatusCancelled
const TaskStatusCompleted
const TaskStatusFailed
const TaskStatusInputRequired
const TaskStatusWorking
TaskStatusNotification is sent when a task's status changes.
Notification Notification
Notification.Method string
Params TaskStatusNotificationParams
func NewTaskStatusNotification(task Task) TaskStatusNotification
Task Task
ISO 8601 timestamp when the task was created.
ISO 8601 timestamp when the task was last updated.
Suggested time in milliseconds between status checks.
Current state of the task execution.
Optional human-readable message describing the current state.
Time in milliseconds from creation before task may be deleted.
If null, the task has no expiration.
Unique identifier for the task.
GetName returns the task ID, implementing the Named interface for pagination.
TaskStatusNotificationParams : Named
TaskSupport indicates how a tool supports task augmentation.
func WithTaskSupport(support TaskSupport) ToolOption
const TaskSupportForbidden
const TaskSupportOptional
const TaskSupportRequired
TextContent represents text provided to or from an LLM.
It must have Type set to "text".
Annotated Annotated
Annotated.Annotations *Annotations
Meta is a metadata object that is reserved by MCP for storing additional information.
The text content of the message.
// Must be "text"
TextContent : Content
func AsTextContent(content any) (*TextContent, bool)
func NewTextContent(text string) TextContent
The MIME type of this resource, if known.
Raw per‑resource metadata; pass‑through as defined by MCP. Not the same as mcp.Meta.
Allows _meta to be used for MCP-UI features for example. Does not assume any specific format.
The text of the item. This must only be set if the item can actually be
represented as text (not binary data).
The URI of this resource.
TextResourceContents : ResourceContents
func AsTextResourceContents(content any) (*TextResourceContents, bool)
Tool represents the definition for a tool the client can call.
Optional properties describing tool behavior
Support for deferred loading
A human-readable description of the tool.
Execution describes execution behavior for the tool
Icons provides visual identifiers for the tool
A JSON Schema object defining the expected parameters for the tool.
Meta is a metadata object that is reserved by MCP for storing additional information.
The name of the tool.
A JSON Schema object defining the expected output returned by the tool .
Alternative to InputSchema - allows arbitrary JSON Schema to be provided
// Hide this from JSON marshaling
Optional JSON Schema defining expected output structure
// Hide this from JSON marshaling
GetName returns the name of the tool.
MarshalJSON implements the json.Marshaler interface for Tool.
It handles marshaling either InputSchema or RawInputSchema based on which is set.
Tool : Named
Tool : github.com/goccy/go-json.Marshaler
Tool : encoding/json.Marshaler
func NewTool(name string, opts ...ToolOption) Tool
func NewToolWithRawSchema(name, description string, schema json.RawMessage) Tool
func NewListToolsResult(tools []Tool, nextCursor Cursor) *ListToolsResult
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddSessionTool(sessionID string, tool Tool, handler server.ToolHandlerFunc) error
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddTaskTool(tool Tool, handler server.TaskToolHandlerFunc)
func github.com/mark3labs/mcp-go/server.(*MCPServer).AddTool(tool Tool, handler server.ToolHandlerFunc)
If true, the tool may perform destructive updates
If true, repeated calls with same args have no additional effect
If true, tool interacts with external entities
If true, the tool does not modify its environment
Human-readable title for the tool
func WithToolAnnotation(annotation ToolAnnotation) ToolOption
ToolArgumentsSchema represents a JSON Schema for tool arguments.
AdditionalProperties any
Defs map[string]any
Properties map[string]any
Required []string
Type string
MarshalJSON implements the json.Marshaler interface for ToolArgumentsSchema.
UnmarshalJSON implements the json.Unmarshaler interface for ToolArgumentsSchema.
ToolArgumentsSchema : github.com/goccy/go-json.Marshaler
*ToolArgumentsSchema : github.com/goccy/go-json.Unmarshaler
ToolArgumentsSchema : encoding/json.Marshaler
*ToolArgumentsSchema : encoding/json.Unmarshaler
ToolExecution describes execution behavior for a tool.
TaskSupport indicates whether the tool supports task augmentation.
AdditionalProperties any
Defs map[string]any
Properties map[string]any
Required []string
Type string
MarshalJSON implements the json.Marshaler interface for ToolInputSchema.
UnmarshalJSON implements the json.Unmarshaler interface for ToolInputSchema.
ToolInputSchema : github.com/goccy/go-json.Marshaler
*ToolInputSchema : github.com/goccy/go-json.Unmarshaler
ToolInputSchema : encoding/json.Marshaler
*ToolInputSchema : encoding/json.Unmarshaler
ToolListChangedNotification is an optional notification from the server to
the client, informing it that the list of tools it offers has changed. This may
be issued by servers without any previous subscription from the client.
Notification Notification
Notification.Method string
Notification.Params NotificationParams
ToolOption is a function that configures a Tool.
It provides a flexible way to set various properties of a Tool using the functional options pattern.
func WithAny(name string, opts ...PropertyOption) ToolOption
func WithArray(name string, opts ...PropertyOption) ToolOption
func WithBoolean(name string, opts ...PropertyOption) ToolOption
func WithDeferLoading(deferLoading bool) ToolOption
func WithDescription(description string) ToolOption
func WithDestructiveHintAnnotation(value bool) ToolOption
func WithIdempotentHintAnnotation(value bool) ToolOption
func WithInputSchema[T]() ToolOption
func WithNumber(name string, opts ...PropertyOption) ToolOption
func WithObject(name string, opts ...PropertyOption) ToolOption
func WithOpenWorldHintAnnotation(value bool) ToolOption
func WithOutputSchema[T]() ToolOption
func WithRawInputSchema(schema json.RawMessage) ToolOption
func WithRawOutputSchema(schema json.RawMessage) ToolOption
func WithReadOnlyHintAnnotation(value bool) ToolOption
func WithSchemaAdditionalProperties(schema any) ToolOption
func WithString(name string, opts ...PropertyOption) ToolOption
func WithTaskSupport(support TaskSupport) ToolOption
func WithTitleAnnotation(title string) ToolOption
func WithToolAnnotation(annotation ToolAnnotation) ToolOption
func WithToolIcons(icons ...Icon) ToolOption
func NewTool(name string, opts ...ToolOption) Tool
AdditionalProperties any
Defs map[string]any
Properties map[string]any
Required []string
Type string
MarshalJSON implements the json.Marshaler interface for ToolOutputSchema.
UnmarshalJSON implements the json.Unmarshaler interface for ToolOutputSchema.
ToolOutputSchema : github.com/goccy/go-json.Marshaler
*ToolOutputSchema : github.com/goccy/go-json.Unmarshaler
ToolOutputSchema : encoding/json.Marshaler
*ToolOutputSchema : encoding/json.Unmarshaler
Type Parameters:
T: any
TypedToolHandlerFunc is a function that handles a tool call with typed arguments
func NewTypedToolHandler[T](handler TypedToolHandlerFunc[T]) func(ctx context.Context, request CallToolRequest) (*CallToolResult, error)
The URI of the resource to subscribe to. The URI can use any protocol; it
is up to the server how to interpret it.
UnsubscribeRequest is sent from the client to request cancellation of
resources/updated notifications from the server. This should follow a previous
resources/subscribe request.
Header http.Header
Params UnsubscribeParams
Request Request
Request.Method string
UnsupportedProtocolVersionError is returned when the server responds with
a protocol version that the client doesn't support.
Version string
( UnsupportedProtocolVersionError) Error() string
Is implements the errors.Is interface for better error handling
UnsupportedProtocolVersionError : error
Template *uritemplate.Template
Expand returns a URI reference corresponding to the template expanded using the passed variables.
(*URITemplate) MarshalJSON() ([]byte, error)
( URITemplate) Match(expansion string) uritemplate.Values
Raw returns a raw URI template passed to New in string.
Regexp converts the template to regexp and returns compiled *regexp.Regexp.
(*URITemplate) UnmarshalJSON(data []byte) error
Varnames returns variable names used in the template.
*URITemplate : github.com/goccy/go-json.Marshaler
*URITemplate : github.com/goccy/go-json.Unmarshaler
*URITemplate : encoding/json.Marshaler
*URITemplate : encoding/json.Unmarshaler
URLElicitationRequiredError is returned when the server requires URL elicitation to proceed.
Elicitations []ElicitationParams
( URLElicitationRequiredError) Error() string
Is implements the errors.Is interface for better error handling
( URLElicitationRequiredError) JSONRPCError() JSONRPCError
URLElicitationRequiredError : error
Package-Level Functions (total 160)
AdditionalProperties specifies whether additional properties are allowed in the object
or defines a schema for additional properties
ArgumentDescription adds a description to a prompt argument.
The description should explain the purpose and expected values of the argument.
AsAudioContent attempts to cast the given interface to AudioContent
AsBlobResourceContents attempts to cast the given interface to BlobResourceContents
AsEmbeddedResource attempts to cast the given interface to EmbeddedResource
AsImageContent attempts to cast the given interface to ImageContent
AsTextContent attempts to cast the given interface to TextContent
AsTextResourceContents attempts to cast the given interface to TextResourceContents
Type Parameters:
T: any
DefaultArray sets the default value for an array property.
This value will be used if the property is not explicitly provided.
DefaultBool sets the default value for a boolean property.
This value will be used if the property is not explicitly provided.
DefaultNumber sets the default value for a number property.
This value will be used if the property is not explicitly provided.
DefaultString sets the default value for a string property.
This value will be used if the property is not explicitly provided.
Description adds a description to a property in the JSON Schema.
The description should explain the purpose and expected values of the property.
Enum specifies a list of allowed values for a string property.
The property value must be one of the specified enum values.
func ExtractString(data map[string]any, key string) string
FormatNumberResult
Helper for formatting numbers in tool results
GetTextFromContent extracts text from a Content interface that might be a TextContent struct
or a map[string]any that was unmarshaled from JSON. This is useful when dealing with content
that comes from different transport layers that may handle JSON differently.
This function uses fallback behavior for non-text content - it returns a string representation
via fmt.Sprintf for any content that cannot be extracted as text. This is a lossy operation
intended for convenience in logging and display scenarios.
For strict type validation, use ParseContent() instead, which returns an error for invalid content.
IsUnsupportedProtocolVersion checks if an error is an UnsupportedProtocolVersionError
Items defines the schema for array items.
Accepts any schema definition for maximum flexibility.
Example:
Items(map[string]any{
"type": "object",
"properties": map[string]any{
"name": map[string]any{"type": "string"},
"age": map[string]any{"type": "number"},
},
})
For simple types, use ItemsString(), ItemsNumber(), ItemsBoolean() instead.
MarshalJSON implements custom JSON marshaling for Content interface
Max sets the maximum value for a number property.
The number value must not exceed this maximum.
MaxItems sets the maximum number of items for an array
MaxLength sets the maximum length for a string property.
The string value must not exceed this length.
MaxProperties sets the maximum number of properties for an object
Min sets the minimum value for a number property.
The number value must not be less than this minimum.
MinItems sets the minimum number of items for an array
MinLength sets the minimum length for a string property.
The string value must be at least this length.
MinProperties sets the minimum number of properties for an object
MultipleOf specifies that a number must be a multiple of the given value.
The number value must be divisible by this value.
Helper function to create a new AudioContent
NewCancelTaskResult creates a CancelTaskResult from a Task.
NewCreateTaskResult creates a CreateTaskResult with the given task.
NewElicitationCompleteNotification creates a new elicitation complete notification.
Helper function to create a new EmbeddedResource
NewGetPromptResult creates a new GetPromptResult
NewGetTaskResult creates a GetTaskResult from a Task.
NewImageContent
Helper function to create a new ImageContent
NewInitializeResult creates a new InitializeResult
NewJSONRPCError creates a new JSONRPCResponse with the given id, code, and message
NewJSONRPCErrorDetails creates a new JSONRPCErrorDetails with the given code, message, and data.
NewJSONRPCResponse creates a new JSONRPCResponse with the given id and result.
NOTE: This function expects a Result struct, but JSONRPCResponse.Result is typed as `any`.
The Result struct wraps the actual result data with optional metadata.
For direct result assignment, use NewJSONRPCResultResponse instead.
NewJSONRPCResultResponse creates a new JSONRPCResponse with the given id and result.
This function accepts any type for the result, matching the JSONRPCResponse.Result field type.
NewListPromptsResult creates a new ListPromptsResult
NewListResourcesResult creates a new ListResourcesResult
NewListResourceTemplatesResult creates a new ListResourceTemplatesResult
NewListTasksResult creates a ListTasksResult with the given tasks.
NewListToolsResult creates a new ListToolsResult
NewLoggingMessageNotification
Helper function for creating a logging message notification
func NewMetaFromMap(m map[string]any) *Meta
NewProgressNotification
Helper function for creating a progress notification
NewPrompt creates a new Prompt with the given name and options.
The prompt will be configured based on the provided options.
Options are applied in order, allowing for flexible prompt configuration.
NewPromptMessage
Helper function to create a new PromptMessage
NewReadResourceResult creates a new ReadResourceResult with text content
NewRequestId creates a new RequestId with the given value
NewResource creates a new Resource with the given URI, name and options.
The resource will be configured based on the provided options.
Options are applied in order, allowing for flexible resource configuration.
Helper function to create a new ResourceLink
NewResourceTemplate creates a new ResourceTemplate with the given URI template, name and options.
The template will be configured based on the provided options.
Options are applied in order, allowing for flexible template configuration.
Type Parameters:
TArgs: any
TResult: any
NewStructuredToolHandler creates a ToolHandlerFunc that automatically binds arguments to a typed struct
and returns structured output. It automatically creates both structured and
text content (from the structured output) for backwards compatibility.
NewTask creates a new Task with the given ID and options.
The task will be configured based on the provided options.
Options are applied in order, allowing for flexible task configuration.
NewTaskParams creates TaskParams with the given TTL.
NewTasksCapability creates a TasksCapability with all operations enabled.
NewTasksCapabilityWithToolsOnly creates a TasksCapability with only tool call support.
List and Cancel operations are not enabled with this capability.
NewTaskStatusNotification creates a notification for a task status change.
NewTextContent
Helper function to create a new TextContent
NewTool creates a new Tool with the given name and options.
The tool will have an object-type input schema with configurable properties.
Options are applied in order, allowing for flexible tool configuration.
NewToolResultAudio creates a new CallToolResult with both text and audio content
NewToolResultError creates a new CallToolResult with an error message.
Any errors that originate from the tool SHOULD be reported inside the result object.
NewToolResultErrorf creates a new CallToolResult with an error message.
The error message is formatted using the fmt package.
Any errors that originate from the tool SHOULD be reported inside the result object.
NewToolResultErrorFromErr creates a new CallToolResult with an error message.
If an error is provided, its details will be appended to the text message.
Any errors that originate from the tool SHOULD be reported inside the result object.
NewToolResultImage creates a new CallToolResult with both text and image content
Type Parameters:
T: any
NewToolResultJSON creates a new CallToolResult with a JSON content.
NewToolResultResource creates a new CallToolResult with an embedded resource
NewToolResultStructured creates a new CallToolResult with structured content.
It includes both the structured content and a text representation for backward compatibility.
NewToolResultStructuredOnly creates a new CallToolResult with structured
content and creates a JSON string fallback for backwards compatibility.
This is useful when you want to provide structured data without any specific text fallback.
NewToolResultText creates a new CallToolResult with a text content
NewToolWithRawSchema creates a new Tool with the given name and a raw JSON
Schema. This allows for arbitrary JSON Schema to be used for the tool's input
schema.
NOTE a [Tool] built in such a way is incompatible with the [ToolOption] and
runtime errors will result from supplying a [ToolOption] to a [Tool] built
with this function.
Type Parameters:
T: any
NewTypedToolHandler creates a ToolHandlerFunc that automatically binds arguments to a typed struct
ParseAnnotations parses priority, audience, and lastModified fields from the provided map
and returns an Annotations struct populated with any valid values found.
If data is nil, ParseAnnotations returns nil. Priority is set when a numeric value can be
parsed and is stored as a *float64. Audience is populated from string values and includes
only RoleUser and RoleAssistant entries. LastModified is set when the value is a string.
func ParseArgument(request CallToolRequest, key string, defaultVal any) any
ParseBoolean extracts and converts a boolean parameter from a CallToolRequest.
If the key is not found in the Arguments map, the defaultValue is returned.
The function uses cast.ToBool for conversion which handles various string representations
such as "true", "yes", "1", etc.
func ParseCallToolResult(rawMessage *json.RawMessage) (*CallToolResult, error)
ParseCancelTaskResult parses a JSON message and converts it to a CancelTaskResult.
ParseContent parses a generic map into a strongly-typed Content value.
It extracts annotations and _meta fields from the map and sets them on
the returned content type.
ParseFloat32 extracts and converts a float32 parameter from a CallToolRequest.
ParseFloat64 extracts and converts a float64 parameter from a CallToolRequest.
func ParseGetPromptResult(rawMessage *json.RawMessage) (*GetPromptResult, error)
ParseGetTaskResult parses a JSON message and converts it to a GetTaskResult.
ParseInt extracts and converts an int parameter from a CallToolRequest.
ParseInt16 extracts and converts an int16 parameter from a CallToolRequest.
ParseInt32 extracts and converts an int32 parameter from a CallToolRequest.
ParseInt64 extracts and converts an int64 parameter from a CallToolRequest.
If the key is not found in the Arguments map, the defaultValue is returned.
ParseInt8 extracts and converts an int8 parameter from a CallToolRequest.
ParseListTasksResult parses a JSON message and converts it to a ListTasksResult.
func ParseReadResourceResult(rawMessage *json.RawMessage) (*ReadResourceResult, error) func ParseResourceContents(contentMap map[string]any) (ResourceContents, error)
ParseString extracts and converts a string parameter from a CallToolRequest.
ParseStringMap extracts and converts a string map parameter from a CallToolRequest.
ParseTaskResultResult parses a JSON message and converts it to a TaskResultResult.
ParseUInt extracts and converts an uint parameter from a CallToolRequest.
ParseUInt16 extracts and converts an uint16 parameter from a CallToolRequest.
ParseUInt32 extracts and converts an uint32 parameter from a CallToolRequest.
ParseUInt64 extracts and converts an uint64 parameter from a CallToolRequest.
ParseUInt8 extracts and converts an uint8 parameter from a CallToolRequest.
Pattern sets a regex pattern that a string property must match.
The string value must conform to the specified regular expression.
Properties sets the "properties" map for an object schema.
The returned PropertyOption stores the provided map under the schema's "properties" key.
PropertyNames defines a schema for property names in an object
RelatedTaskMeta creates the metadata for associating a message with a task.
The returned map contains a "taskId" field with the provided task ID.
Required marks a property as required in the tool's input schema.
Required properties must be provided when using the tool.
RequiredArgument marks an argument as required in the prompt.
Required arguments must be provided when getting the prompt.
Title adds a display-friendly title to a property in the JSON Schema.
This title can be used by UI components to show a more readable property name.
ToBoolPtr returns a pointer to the given boolean value
ToInt64Ptr returns a pointer to the given int64 value
UniqueItems specifies whether array items must be unique
UnmarshalContent implements custom JSON unmarshaling for Content interface
ValidateISO8601Timestamp verifies that timestamp is a valid ISO 8601 timestamp
using the RFC3339 layout. An empty string is considered valid. It returns nil
when the timestamp is valid, or the parsing error when it is not.
WithAnnotations returns a ResourceOption that sets the resource's Annotations fields.
It initializes Annotations if nil, sets Audience to the provided slice,
stores Priority as a pointer to the provided value, and sets LastModified to the provided timestamp.
WithAny adds an input property named name with no predefined JSON Schema type to the Tool's input schema.
The returned ToolOption applies the provided PropertyOption functions to the property's schema, moves a property-level
`required` flag into the Tool's InputSchema.Required list if present, and stores the resulting schema under InputSchema.Properties[name].
WithArgument adds an argument to the prompt's argument list.
The argument will be configured based on the provided options.
WithArray returns a ToolOption that adds an array-typed property with the given name to a Tool's input schema.
It applies provided PropertyOption functions to configure the property's schema, moves a `required` flag
from the property schema into the Tool's InputSchema.Required slice when present, and registers the resulting
schema under InputSchema.Properties[name].
WithBoolean adds a boolean property to the tool schema.
It accepts property options to configure the boolean property's behavior and constraints.
WithBooleanItems configures an array's items to be of type boolean.
Supported options: Description(), DefaultBool()
Note: Options like Required() are not valid for item schemas and will be ignored.
Examples:
mcp.WithArray("flags", mcp.WithBooleanItems())
mcp.WithArray("permissions", mcp.WithBooleanItems(mcp.Description("User permissions")))
Limitations: Only supports simple boolean arrays. Use Items() for complex objects.
WithDeferLoading sets the defer_loading flag for the tool.
This is used to implement dynamic tool loading/searching patterns.
WithDescription adds a description to the Tool.
The description should provide a clear, human-readable explanation of what the tool does.
WithDestructiveHintAnnotation sets the DestructiveHint field of the Tool's Annotations.
If true, it indicates the tool may perform destructive updates.
WithIdempotentHintAnnotation sets the IdempotentHint field of the Tool's Annotations.
If true, it indicates repeated calls with the same arguments have no additional effect.
Type Parameters:
T: any
WithInputSchema creates a ToolOption that sets the input schema for a tool.
It accepts any Go type, usually a struct, and automatically generates a JSON schema from it.
WithLastModified returns a ResourceOption that sets the resource's Annotations.LastModified
to the provided timestamp. If the resource's Annotations is nil, it will be initialized.
The timestamp is expected to be an ISO 8601 (RFC3339) formatted string (e.g., "2025-01-12T15:00:58Z").
WithMIMEType sets the MIME type for the Resource.
This should indicate the format of the resource's contents.
WithModelImmediateResponse creates Meta with an immediate response message for the model.
This allows the model to continue processing while the task executes asynchronously.
The message parameter is a human-readable string that will be shown to the model.
Example:
return &mcp.CreateTaskResult{
Task: task,
Result: mcp.Result{
Meta: mcp.WithModelImmediateResponse("Processing your request. This may take a few minutes."),
},
}
WithNumber adds a number property to the tool schema.
It accepts property options to configure the number property's behavior and constraints.
WithNumberItems configures an array's items to be of type number.
Supported options: Description(), DefaultNumber(), Min(), Max(), MultipleOf()
Note: Options like Required() are not valid for item schemas and will be ignored.
Examples:
mcp.WithArray("scores", mcp.WithNumberItems(mcp.Min(0), mcp.Max(100)))
mcp.WithArray("prices", mcp.WithNumberItems(mcp.Min(0)))
Limitations: Only supports simple number arrays. Use Items() for complex objects.
WithObject adds an object property to the tool schema.
It accepts property options to configure the object property's behavior and constraints.
WithOpenWorldHintAnnotation sets the OpenWorldHint field of the Tool's Annotations.
If true, it indicates the tool interacts with external entities.
Type Parameters:
T: any
WithOutputSchema creates a ToolOption that sets the output schema for a tool.
It accepts any Go type, usually a struct, and automatically generates a JSON schema from it.
WithPromptDescription adds a description to the Prompt.
The description should provide a clear, human-readable explanation of what the prompt does.
WithPromptIcons adds icons to the Prompt.
Icons provide visual identifiers for the prompt.
WithRawInputSchema sets a raw JSON schema for the tool's input.
Use this when you need full control over the schema or when working with
complex schemas that can't be generated from Go types. The jsonschema library
can handle complex schemas and provides nice extension points, so be sure to
check that out before using this.
WithRawOutputSchema sets a raw JSON schema for the tool's output.
Use this when you need full control over the schema or when working with
complex schemas that can't be generated from Go types. The jsonschema library
can handle complex schemas and provides nice extension points, so be sure to
check that out before using this.
WithReadOnlyHintAnnotation sets the ReadOnlyHint field of the Tool's Annotations.
If true, it indicates the tool does not modify its environment.
WithRelatedTask returns a Meta with the related task ID set.
This is useful for associating task results with their originating task.
WithResourceDescription adds a description to the Resource.
The description should provide a clear, human-readable explanation of what the resource represents.
WithResourceIcons adds icons to the Resource.
Icons provide visual identifiers for the resource.
WithSchemaAdditionalProperties sets the additionalProperties field on the tool's input schema.
It accepts false (disallow extra properties), true (allow any), or a schema map
to validate additional properties against.
WithString adds a string property to the tool schema.
It accepts property options to configure the string property's behavior and constraints.
WithStringEnumItems configures an array's items to be of type string with a specified enum.
Example:
mcp.WithArray("priority", mcp.WithStringEnumItems([]string{"low", "medium", "high"}))
Limitations: Only supports string enums. Use WithStringItems(Enum(...)) for more flexibility.
WithStringItems configures an array's items to be of type string.
Supported options: Description(), DefaultString(), Enum(), MaxLength(), MinLength(), Pattern()
Note: Options like Required() are not valid for item schemas and will be ignored.
Examples:
mcp.WithArray("tags", mcp.WithStringItems())
mcp.WithArray("colors", mcp.WithStringItems(mcp.Enum("red", "green", "blue")))
mcp.WithArray("names", mcp.WithStringItems(mcp.MinLength(1), mcp.MaxLength(50)))
Limitations: Only supports simple string arrays. Use Items() for complex objects.
WithTaskCreatedAt sets a specific creation timestamp for the task.
By default, NewTask uses the current time.
WithTaskPollInterval sets the suggested polling interval in milliseconds.
WithTaskStatus sets the status of the task.
WithTaskStatusMessage sets a human-readable status message for the task.
WithTaskSupport sets the task support mode for the tool.
It configures whether the tool can be invoked as a task (asynchronously).
Valid values are TaskSupportForbidden (default), TaskSupportOptional, or TaskSupportRequired.
WithTaskTTL sets the time-to-live for the task in milliseconds.
After this duration from creation, the task may be deleted.
WithTemplateAnnotations returns a ResourceTemplateOption that sets the template's
Annotations field, initializing it if nil, and setting Audience, Priority, and LastModified.
WithTemplateDescription adds a description to the ResourceTemplate.
The description should provide a clear, human-readable explanation of what resources this template represents.
WithTemplateIcons adds icons to the ResourceTemplate.
Icons provide visual identifiers for the resource template.
WithTemplateMIMEType sets the MIME type for the ResourceTemplate.
This should only be set if all resources matching this template will have the same type.
WithTitleAnnotation sets the Title field of the Tool's Annotations.
It provides a human-readable title for the tool.
WithToolAnnotation adds optional hints about the Tool.
WithToolIcons adds icons to the Tool.
Icons provide visual identifiers for the tool.
Package-Level Variables (total 8)
ErrInternalError indicates an internal JSON-RPC error (code: INTERNAL_ERROR).
ErrInvalidParams indicates invalid method parameters (code: INVALID_PARAMS).
ErrInvalidRequest indicates an invalid JSON-RPC request (code: INVALID_REQUEST).
ErrMethodNotFound indicates the requested method does not exist (code: METHOD_NOT_FOUND).
ErrParseError indicates a JSON parsing error (code: PARSE_ERROR).
ErrRequestInterrupted indicates a request was cancelled or timed out (code: REQUEST_INTERRUPTED).
ErrResourceNotFound indicates a requested resource was not found (code: RESOURCE_NOT_FOUND).
ValidProtocolVersions lists all known valid MCP protocol versions.
Package-Level Constants (total 65)
const ContentTypeAudio = "audio" const ContentTypeImage = "image" const ContentTypeLink = "resource_link" const ContentTypeResource = "resource" const ContentTypeText = "text" const ElicitationModeForm = "form" const ElicitationModeURL = "url"
ElicitationResponseActionAccept indicates the user provided the requested information.
ElicitationResponseActionCancel indicates the user cancelled without making a choice.
ElicitationResponseActionDecline indicates the user explicitly declined to provide information.
INTERNAL_ERROR indicates internal JSON-RPC error.
INVALID_PARAMS indicates invalid method parameter(s).
INVALID_REQUEST indicates the JSON sent is not a valid Request object.
JSONRPC_VERSION is the version of JSON-RPC used by MCP.
LATEST_PROTOCOL_VERSION is the most recent version of the MCP protocol.
const LoggingLevelAlert LoggingLevel = "alert" const LoggingLevelCritical LoggingLevel = "critical" const LoggingLevelDebug LoggingLevel = "debug" const LoggingLevelEmergency LoggingLevel = "emergency" const LoggingLevelError LoggingLevel = "error" const LoggingLevelInfo LoggingLevel = "info" const LoggingLevelNotice LoggingLevel = "notice" const LoggingLevelWarning LoggingLevel = "warning"
METHOD_NOT_FOUND indicates the method does not exist/is not available.
MethodCompletionComplete returns completion suggestions for a given argument
https://modelcontextprotocol.io/specification/2025-11-25/server/utilities/completion
MethodElicitationCreate requests additional information from the user during interactions.
https://modelcontextprotocol.io/docs/concepts/elicitation
MethodInitialize initiates connection and negotiates protocol capabilities.
https://modelcontextprotocol.io/specification/2024-11-05/basic/lifecycle/#initialization
MethodListRoots requests roots list from the client during interactions.
https://modelcontextprotocol.io/specification/2025-06-18/client/roots
MethodNotificationElicitationComplete notifies when a URL mode elicitation completes.
MethodNotificationPromptsListChanged notifies when the list of available prompt templates changes.
https://modelcontextprotocol.io/specification/2025-03-26/server/prompts#list-changed-notification
MethodNotificationResourcesListChanged notifies when the list of available resources changes.
https://modelcontextprotocol.io/specification/2025-03-26/server/resources#list-changed-notification
const MethodNotificationResourceUpdated = "notifications/resources/updated"
MethodNotificationRootsListChanged notifies when the list of available roots changes.
https://modelcontextprotocol.io/specification/2025-06-18/client/roots#root-list-changes
MethodNotificationTasksStatus notifies when a task's status changes.
https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/tasks
MethodNotificationToolsListChanged notifies when the list of available tools changes.
https://modelcontextprotocol.io/specification/2025-06-18/server/tools#list-changed-notification
MethodPing verifies connection liveness between client and server.
https://modelcontextprotocol.io/specification/2024-11-05/basic/utilities/ping/
MethodPromptsGet retrieves a specific prompt template with filled parameters.
https://modelcontextprotocol.io/specification/2024-11-05/server/prompts/
MethodPromptsList lists all available prompt templates.
https://modelcontextprotocol.io/specification/2024-11-05/server/prompts/
MethodResourcesList lists all available server resources.
https://modelcontextprotocol.io/specification/2024-11-05/server/resources/
MethodResourcesRead retrieves content of a specific resource by URI.
https://modelcontextprotocol.io/specification/2024-11-05/server/resources/
MethodResourcesTemplatesList provides URI templates for constructing resource URIs.
https://modelcontextprotocol.io/specification/2024-11-05/server/resources/
MethodSamplingCreateMessage allows servers to request LLM completions from clients
MethodSetLogLevel configures the minimum log level for client
https://modelcontextprotocol.io/specification/2025-03-26/server/utilities/logging
MethodTasksCancel cancels an in-progress task.
https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/tasks
MethodTasksGet retrieves the current status of a task.
https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/tasks
MethodTasksList lists all tasks for the current session.
https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/tasks
MethodTasksResult retrieves the result of a completed task.
https://modelcontextprotocol.io/specification/2025-11-25/basic/utilities/tasks
MethodToolsCall invokes a specific tool with provided parameters.
https://modelcontextprotocol.io/specification/2024-11-05/server/tools/
MethodToolsList lists all available executable tools.
https://modelcontextprotocol.io/specification/2024-11-05/server/tools/
ModelImmediateResponseMetaKey is the metadata key for providing an immediate response to the model.
Servers can use this optional key in the _meta field of CreateTaskResult to provide
a string that should be passed as an immediate tool result to the model while the task
continues executing asynchronously in the background.
PARSE_ERROR indicates invalid JSON was received by the server.
RelatedTaskMetaKey is the metadata key for associating a message with a task.
REQUEST_INTERRUPTED indicates a request was cancelled or timed out.
RESOURCE_NOT_FOUND indicates that the requested resource was not found.
const RoleAssistant Role = "assistant"
TaskStatusCancelled indicates the request was cancelled before completion.
TaskStatusCompleted indicates the request completed successfully.
TaskStatusFailed indicates the request did not complete successfully.
TaskStatusInputRequired indicates the receiver needs input from the requestor.
NOTE: This status is defined by the spec but not yet implemented in this SDK.
The input_required flow requires integration with elicitation which is planned
for a future release.
TaskStatusWorking indicates the request is currently being processed.
TaskSupportForbidden means the tool cannot be invoked as a task (default).
TaskSupportOptional means the tool can be invoked as a task or normally.
TaskSupportRequired means the tool must be invoked as a task.
URL_ELICITATION_REQUIRED is the error code for when URL elicitation is required.
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