go-sdk/mcp/protocol.go
awschmeder c6e7337e7e fix: add JSON tags to ElicitationCapabilities fields
The Form and URL fields in ElicitationCapabilities were missing JSON
struct tags, causing them to serialize as "Form" and "URL" (capitalized)
instead of the lowercase "form" and "url" required by the MCP protocol.

This caused initialization failures when clients advertised elicitation
capabilities, as servers would not recognize the incorrectly-cased keys.

Discovered via downstream issue: https://github.com/docker/cagent/issues/1574
2026-02-03 16:27:48 +01:00

1357 lines
54 KiB
Go

// Copyright 2025 The Go MCP SDK Authors. All rights reserved.
// Use of this source code is governed by an MIT-style
// license that can be found in the LICENSE file.
package mcp
// Protocol types for version 2025-06-18.
// To see the schema changes from the previous version, run:
//
// prefix=https://raw.githubusercontent.com/modelcontextprotocol/modelcontextprotocol/refs/heads/main/schema
// sdiff -l <(curl $prefix/2025-03-26/schema.ts) <(curl $prefix/2025/06-18/schema.ts)
import (
"encoding/json"
"fmt"
)
// Optional annotations for the client. The client can use annotations to inform
// how objects are used or displayed.
type Annotations struct {
// 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., []Role{"user", "assistant"}).
Audience []Role `json:"audience,omitempty"`
// The moment the resource was last modified, as an ISO 8601 formatted string.
//
// Should be an ISO 8601 formatted string (e.g., "2025-01-12T15:00:58Z").
//
// Examples: last activity timestamp in an open file, timestamp when the
// resource was attached, etc.
LastModified string `json:"lastModified,omitempty"`
// 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 float64 `json:"priority,omitempty"`
}
// CallToolParams is used by clients to call a tool.
type CallToolParams struct {
// Meta is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// Name is the name of the tool to call.
Name string `json:"name"`
// Arguments holds the tool arguments. It can hold any value that can be
// marshaled to JSON.
Arguments any `json:"arguments,omitempty"`
}
// CallToolParamsRaw is passed to tool handlers on the server. Its arguments
// are not yet unmarshaled (hence "raw"), so that the handlers can perform
// unmarshaling themselves.
type CallToolParamsRaw struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// Name is the name of the tool being called.
Name string `json:"name"`
// Arguments is the raw arguments received over the wire from the client. It
// is the responsibility of the tool handler to unmarshal and validate the
// Arguments (see [AddTool]).
Arguments json.RawMessage `json:"arguments,omitempty"`
}
// A CallToolResult is the server's response to a tool call.
//
// The [ToolHandler] and [ToolHandlerFor] handler functions return this result,
// though [ToolHandlerFor] populates much of it automatically as documented at
// each field.
type CallToolResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// A list of content objects that represent the unstructured result of the tool
// call.
//
// When using a [ToolHandlerFor] with structured output, if Content is unset
// it will be populated with JSON text content corresponding to the
// structured output value.
Content []Content `json:"content"`
// StructuredContent is an optional value that represents the structured
// result of the tool call. It must marshal to a JSON object.
//
// When using a [ToolHandlerFor] with structured output, you should not
// populate this field. It will be automatically populated with the typed Out
// value.
StructuredContent any `json:"structuredContent,omitempty"`
// IsError reports whether the tool call ended in an error.
//
// If not set, this is assumed to be false (the call was successful).
//
// Any errors that originate from the tool should be reported inside the
// Content field, 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.
//
// When using a [ToolHandlerFor], this field is automatically set when the
// tool handler returns an error, and the error string is included as text in
// the Content field.
IsError bool `json:"isError,omitempty"`
// The error passed to setError, if any.
// It is not marshaled, and therefore it is only visible on the server.
// Its only use is in server sending middleware, where it can be accessed
// with getError.
err error
}
// SetError sets the error for the tool result and populates the Content field
// with the error text. It also sets IsError to true.
func (r *CallToolResult) SetError(err error) {
r.Content = []Content{&TextContent{Text: err.Error()}}
r.IsError = true
r.err = err
}
// GetError returns the error set with SetError, or nil if none.
// This function always returns nil on clients.
func (r *CallToolResult) GetError() error {
return r.err
}
func (*CallToolResult) isResult() {}
// UnmarshalJSON handles the unmarshalling of content into the Content
// interface.
func (x *CallToolResult) UnmarshalJSON(data []byte) error {
type res CallToolResult // avoid recursion
var wire struct {
res
Content []*wireContent `json:"content"`
}
if err := json.Unmarshal(data, &wire); err != nil {
return err
}
var err error
if wire.res.Content, err = contentsFromWire(wire.Content, nil); err != nil {
return err
}
*x = CallToolResult(wire.res)
return nil
}
func (x *CallToolParams) isParams() {}
func (x *CallToolParams) GetProgressToken() any { return getProgressToken(x) }
func (x *CallToolParams) SetProgressToken(t any) { setProgressToken(x, t) }
func (x *CallToolParamsRaw) isParams() {}
func (x *CallToolParamsRaw) GetProgressToken() any { return getProgressToken(x) }
func (x *CallToolParamsRaw) SetProgressToken(t any) { setProgressToken(x, t) }
type CancelledParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An optional string describing the reason for the cancellation. This may be
// logged or presented to the user.
Reason string `json:"reason,omitempty"`
// The ID of the request to cancel.
//
// This must correspond to the ID of a request previously issued in the same
// direction.
RequestID any `json:"requestId"`
}
func (x *CancelledParams) isParams() {}
func (x *CancelledParams) GetProgressToken() any { return getProgressToken(x) }
func (x *CancelledParams) SetProgressToken(t any) { setProgressToken(x, t) }
// RootCapabilities describes a client's support for roots.
type RootCapabilities struct {
// ListChanged reports whether the client supports notifications for
// changes to the roots list.
ListChanged bool `json:"listChanged,omitempty"`
}
// 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.
type ClientCapabilities struct {
// NOTE: any addition to ClientCapabilities must also be reflected in
// [ClientCapabilities.clone].
// Experimental reports non-standard capabilities that the client supports.
Experimental map[string]any `json:"experimental,omitempty"`
// Roots describes the client's support for roots.
//
// Deprecated: use RootsV2. As described in #607, Roots should have been a
// pointer to a RootCapabilities value. Roots will be continue to be
// populated, but any new fields will only be added in the RootsV2 field.
Roots struct {
// ListChanged reports whether the client supports notifications for
// changes to the roots list.
ListChanged bool `json:"listChanged,omitempty"`
} `json:"roots,omitempty"`
// RootsV2 is present if the client supports roots. When capabilities are explicitly configured via [ClientOptions.Capabilities]
RootsV2 *RootCapabilities `json:"-"`
// Sampling is present if the client supports sampling from an LLM.
Sampling *SamplingCapabilities `json:"sampling,omitempty"`
// Elicitation is present if the client supports elicitation from the server.
Elicitation *ElicitationCapabilities `json:"elicitation,omitempty"`
}
// clone returns a deep copy of the ClientCapabilities.
func (c *ClientCapabilities) clone() *ClientCapabilities {
cp := *c
cp.RootsV2 = shallowClone(c.RootsV2)
cp.Sampling = shallowClone(c.Sampling)
if c.Elicitation != nil {
x := *c.Elicitation
x.Form = shallowClone(c.Elicitation.Form)
x.URL = shallowClone(c.Elicitation.URL)
cp.Elicitation = &x
}
return &cp
}
// shallowClone returns a shallow clone of *p, or nil if p is nil.
func shallowClone[T any](p *T) *T {
if p == nil {
return nil
}
x := *p
return &x
}
func (c *ClientCapabilities) toV2() *clientCapabilitiesV2 {
return &clientCapabilitiesV2{
ClientCapabilities: *c,
Roots: c.RootsV2,
}
}
// clientCapabilitiesV2 is a version of ClientCapabilities that fixes the bug
// described in #607: Roots should have been a pointer to value type
// RootCapabilities.
type clientCapabilitiesV2 struct {
ClientCapabilities
Roots *RootCapabilities `json:"roots,omitempty"`
}
func (c *clientCapabilitiesV2) toV1() *ClientCapabilities {
caps := c.ClientCapabilities
caps.RootsV2 = c.Roots
// Sync Roots from RootsV2 for backward compatibility (#607).
if caps.RootsV2 != nil {
caps.Roots = *caps.RootsV2
}
return &caps
}
type CompleteParamsArgument struct {
// The name of the argument
Name string `json:"name"`
// The value of the argument to use for completion matching.
Value string `json:"value"`
}
// CompleteContext represents additional, optional context for completions.
type CompleteContext struct {
// Previously-resolved variables in a URI template or prompt.
Arguments map[string]string `json:"arguments,omitempty"`
}
// CompleteReference represents a completion reference type (ref/prompt ref/resource).
// The Type field determines which other fields are relevant.
type CompleteReference struct {
Type string `json:"type"`
// Name is relevant when Type is "ref/prompt".
Name string `json:"name,omitempty"`
// URI is relevant when Type is "ref/resource".
URI string `json:"uri,omitempty"`
}
func (r *CompleteReference) UnmarshalJSON(data []byte) error {
type wireCompleteReference CompleteReference // for naive unmarshaling
var r2 wireCompleteReference
if err := json.Unmarshal(data, &r2); err != nil {
return err
}
switch r2.Type {
case "ref/prompt", "ref/resource":
if r2.Type == "ref/prompt" && r2.URI != "" {
return fmt.Errorf("reference of type %q must not have a URI set", r2.Type)
}
if r2.Type == "ref/resource" && r2.Name != "" {
return fmt.Errorf("reference of type %q must not have a Name set", r2.Type)
}
default:
return fmt.Errorf("unrecognized content type %q", r2.Type)
}
*r = CompleteReference(r2)
return nil
}
func (r *CompleteReference) MarshalJSON() ([]byte, error) {
// Validation for marshalling: ensure consistency before converting to JSON.
switch r.Type {
case "ref/prompt":
if r.URI != "" {
return nil, fmt.Errorf("reference of type %q must not have a URI set for marshalling", r.Type)
}
case "ref/resource":
if r.Name != "" {
return nil, fmt.Errorf("reference of type %q must not have a Name set for marshalling", r.Type)
}
default:
return nil, fmt.Errorf("unrecognized reference type %q for marshalling", r.Type)
}
type wireReference CompleteReference
return json.Marshal(wireReference(*r))
}
type CompleteParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The argument's information
Argument CompleteParamsArgument `json:"argument"`
Context *CompleteContext `json:"context,omitempty"`
Ref *CompleteReference `json:"ref"`
}
func (*CompleteParams) isParams() {}
type CompletionResultDetails struct {
HasMore bool `json:"hasMore,omitempty"`
Total int `json:"total,omitempty"`
Values []string `json:"values"`
}
// The server's response to a completion/complete request
type CompleteResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
Completion CompletionResultDetails `json:"completion"`
}
func (*CompleteResult) isResult() {}
type CreateMessageParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// A request to include context from one or more MCP servers (including the
// caller), to be attached to the prompt. The client may ignore this request.
IncludeContext string `json:"includeContext,omitempty"`
// The maximum number of tokens to sample, as requested by the server. The
// client may choose to sample fewer tokens than requested.
MaxTokens int64 `json:"maxTokens"`
Messages []*SamplingMessage `json:"messages"`
// Optional metadata to pass through to the LLM provider. The format of this
// metadata is provider-specific.
Metadata any `json:"metadata,omitempty"`
// The server's preferences for which model to select. The client may ignore
// these preferences.
ModelPreferences *ModelPreferences `json:"modelPreferences,omitempty"`
StopSequences []string `json:"stopSequences,omitempty"`
// An optional system prompt the server wants to use for sampling. The client
// may modify or omit this prompt.
SystemPrompt string `json:"systemPrompt,omitempty"`
Temperature float64 `json:"temperature,omitempty"`
}
func (x *CreateMessageParams) isParams() {}
func (x *CreateMessageParams) GetProgressToken() any { return getProgressToken(x) }
func (x *CreateMessageParams) SetProgressToken(t any) { setProgressToken(x, t) }
// 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.
type CreateMessageResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
Content Content `json:"content"`
// The name of the model that generated the message.
Model string `json:"model"`
Role Role `json:"role"`
// The reason why sampling stopped, if known.
StopReason string `json:"stopReason,omitempty"`
}
func (*CreateMessageResult) isResult() {}
func (r *CreateMessageResult) UnmarshalJSON(data []byte) error {
type result CreateMessageResult // avoid recursion
var wire struct {
result
Content *wireContent `json:"content"`
}
if err := json.Unmarshal(data, &wire); err != nil {
return err
}
var err error
if wire.result.Content, err = contentFromWire(wire.Content, map[string]bool{"text": true, "image": true, "audio": true}); err != nil {
return err
}
*r = CreateMessageResult(wire.result)
return nil
}
type GetPromptParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// Arguments to use for templating the prompt.
Arguments map[string]string `json:"arguments,omitempty"`
// The name of the prompt or prompt template.
Name string `json:"name"`
}
func (x *GetPromptParams) isParams() {}
func (x *GetPromptParams) GetProgressToken() any { return getProgressToken(x) }
func (x *GetPromptParams) SetProgressToken(t any) { setProgressToken(x, t) }
// The server's response to a prompts/get request from the client.
type GetPromptResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An optional description for the prompt.
Description string `json:"description,omitempty"`
Messages []*PromptMessage `json:"messages"`
}
func (*GetPromptResult) isResult() {}
// InitializeParams is sent by the client to initialize the session.
type InitializeParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// Capabilities describes the client's capabilities.
Capabilities *ClientCapabilities `json:"capabilities"`
// ClientInfo provides information about the client.
ClientInfo *Implementation `json:"clientInfo"`
// ProtocolVersion is the latest version of the Model Context Protocol that
// the client supports.
ProtocolVersion string `json:"protocolVersion"`
}
func (p *InitializeParams) toV2() *initializeParamsV2 {
return &initializeParamsV2{
InitializeParams: *p,
Capabilities: p.Capabilities.toV2(),
}
}
// initializeParamsV2 works around the mistake in #607: Capabilities.Roots
// should have been a pointer.
type initializeParamsV2 struct {
InitializeParams
Capabilities *clientCapabilitiesV2 `json:"capabilities"`
}
func (p *initializeParamsV2) toV1() *InitializeParams {
p1 := p.InitializeParams
if p.Capabilities != nil {
p1.Capabilities = p.Capabilities.toV1()
}
return &p1
}
func (x *InitializeParams) isParams() {}
func (x *InitializeParams) GetProgressToken() any { return getProgressToken(x) }
func (x *InitializeParams) SetProgressToken(t any) { setProgressToken(x, t) }
// InitializeResult is sent by the server in response to an initialize request
// from the client.
type InitializeResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// Capabilities describes the server's capabilities.
Capabilities *ServerCapabilities `json:"capabilities"`
// 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.
Instructions string `json:"instructions,omitempty"`
// 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.
ProtocolVersion string `json:"protocolVersion"`
ServerInfo *Implementation `json:"serverInfo"`
}
func (*InitializeResult) isResult() {}
type InitializedParams struct {
// Meta is reserved by the protocol to allow clients and servers to attach
// additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
func (x *InitializedParams) isParams() {}
func (x *InitializedParams) GetProgressToken() any { return getProgressToken(x) }
func (x *InitializedParams) SetProgressToken(t any) { setProgressToken(x, t) }
type ListPromptsParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the current pagination position. If provided,
// the server should return results starting after this cursor.
Cursor string `json:"cursor,omitempty"`
}
func (x *ListPromptsParams) isParams() {}
func (x *ListPromptsParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ListPromptsParams) SetProgressToken(t any) { setProgressToken(x, t) }
func (x *ListPromptsParams) cursorPtr() *string { return &x.Cursor }
// The server's response to a prompts/list request from the client.
type ListPromptsResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the pagination position after the last returned
// result. If present, there may be more results available.
NextCursor string `json:"nextCursor,omitempty"`
Prompts []*Prompt `json:"prompts"`
}
func (x *ListPromptsResult) isResult() {}
func (x *ListPromptsResult) nextCursorPtr() *string { return &x.NextCursor }
type ListResourceTemplatesParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the current pagination position. If provided,
// the server should return results starting after this cursor.
Cursor string `json:"cursor,omitempty"`
}
func (x *ListResourceTemplatesParams) isParams() {}
func (x *ListResourceTemplatesParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ListResourceTemplatesParams) SetProgressToken(t any) { setProgressToken(x, t) }
func (x *ListResourceTemplatesParams) cursorPtr() *string { return &x.Cursor }
// The server's response to a resources/templates/list request from the client.
type ListResourceTemplatesResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the pagination position after the last returned
// result. If present, there may be more results available.
NextCursor string `json:"nextCursor,omitempty"`
ResourceTemplates []*ResourceTemplate `json:"resourceTemplates"`
}
func (x *ListResourceTemplatesResult) isResult() {}
func (x *ListResourceTemplatesResult) nextCursorPtr() *string { return &x.NextCursor }
type ListResourcesParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the current pagination position. If provided,
// the server should return results starting after this cursor.
Cursor string `json:"cursor,omitempty"`
}
func (x *ListResourcesParams) isParams() {}
func (x *ListResourcesParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ListResourcesParams) SetProgressToken(t any) { setProgressToken(x, t) }
func (x *ListResourcesParams) cursorPtr() *string { return &x.Cursor }
// The server's response to a resources/list request from the client.
type ListResourcesResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the pagination position after the last returned
// result. If present, there may be more results available.
NextCursor string `json:"nextCursor,omitempty"`
Resources []*Resource `json:"resources"`
}
func (x *ListResourcesResult) isResult() {}
func (x *ListResourcesResult) nextCursorPtr() *string { return &x.NextCursor }
type ListRootsParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
func (x *ListRootsParams) isParams() {}
func (x *ListRootsParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ListRootsParams) SetProgressToken(t any) { setProgressToken(x, t) }
// 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.
type ListRootsResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
Roots []*Root `json:"roots"`
}
func (*ListRootsResult) isResult() {}
type ListToolsParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the current pagination position. If provided,
// the server should return results starting after this cursor.
Cursor string `json:"cursor,omitempty"`
}
func (x *ListToolsParams) isParams() {}
func (x *ListToolsParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ListToolsParams) SetProgressToken(t any) { setProgressToken(x, t) }
func (x *ListToolsParams) cursorPtr() *string { return &x.Cursor }
// The server's response to a tools/list request from the client.
type ListToolsResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// An opaque token representing the pagination position after the last returned
// result. If present, there may be more results available.
NextCursor string `json:"nextCursor,omitempty"`
Tools []*Tool `json:"tools"`
}
func (x *ListToolsResult) isResult() {}
func (x *ListToolsResult) nextCursorPtr() *string { return &x.NextCursor }
// 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
type LoggingLevel string
type LoggingMessageParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The data to be logged, such as a string message or an object. Any JSON
// serializable type is allowed here.
Data any `json:"data"`
// The severity of this log message.
Level LoggingLevel `json:"level"`
// An optional name of the logger issuing this message.
Logger string `json:"logger,omitempty"`
}
func (x *LoggingMessageParams) isParams() {}
func (x *LoggingMessageParams) GetProgressToken() any { return getProgressToken(x) }
func (x *LoggingMessageParams) SetProgressToken(t any) { setProgressToken(x, t) }
// 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.
type ModelHint struct {
// 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`
Name string `json:"name,omitempty"`
}
// The server's preferences for model selection, requested of the client during
// sampling.
//
// Because LLMs can vary along multiple dimensions, choosing the "best" model is
// 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.
type ModelPreferences struct {
// 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.
CostPriority float64 `json:"costPriority,omitempty"`
// 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.
Hints []*ModelHint `json:"hints,omitempty"`
// 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.
IntelligencePriority float64 `json:"intelligencePriority,omitempty"`
// 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.
SpeedPriority float64 `json:"speedPriority,omitempty"`
}
type PingParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
func (x *PingParams) isParams() {}
func (x *PingParams) GetProgressToken() any { return getProgressToken(x) }
func (x *PingParams) SetProgressToken(t any) { setProgressToken(x, t) }
type ProgressNotificationParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The progress token which was given in the initial request, used to associate
// this notification with the request that is proceeding.
ProgressToken any `json:"progressToken"`
// An optional message describing the current progress.
Message string `json:"message,omitempty"`
// The progress thus far. This should increase every time progress is made, even
// if the total is unknown.
Progress float64 `json:"progress"`
// Total number of items to process (or total progress required), if known.
// Zero means unknown.
Total float64 `json:"total,omitempty"`
}
func (*ProgressNotificationParams) isParams() {}
// IconTheme specifies the theme an icon is designed for.
type IconTheme string
const (
// IconThemeLight indicates the icon is designed for a light background.
IconThemeLight IconTheme = "light"
// IconThemeDark indicates the icon is designed for a dark background.
IconThemeDark IconTheme = "dark"
)
// Icon provides visual identifiers for their resources, tools, prompts, and implementations
// See [/specification/draft/basic/index#icons] for notes on icons
//
// TODO(iamsurajbobade): update specification url from draft.
type Icon struct {
// Source is A URI pointing to the icon resource (required). This can be:
// - An HTTP/HTTPS URL pointing to an image file
// - A data URI with base64-encoded image data
Source string `json:"src"`
// Optional MIME type if the server's type is missing or generic
MIMEType string `json:"mimeType,omitempty"`
// Optional size specification (e.g., ["48x48"], ["any"] for scalable formats like SVG, or ["48x48", "96x96"] for multiple sizes)
Sizes []string `json:"sizes,omitempty"`
// Optional theme specifier. "light" indicates the icon is designed for a light
// background, "dark" indicates the icon is designed for a dark background.
Theme IconTheme `json:"theme,omitempty"`
}
// A prompt or prompt template that the server offers.
type Prompt struct {
// See [specification/2025-06-18/basic/index#general-fields] for notes on _meta
// usage.
Meta `json:"_meta,omitempty"`
// A list of arguments to use for templating the prompt.
Arguments []*PromptArgument `json:"arguments,omitempty"`
// An optional description of what this prompt provides
Description string `json:"description,omitempty"`
// Intended for programmatic or logical use, but used as a display name in past
// specs or fallback (if title isn't present).
Name string `json:"name"`
// Intended for UI and end-user contexts — optimized to be human-readable and
// easily understood, even by those unfamiliar with domain-specific terminology.
Title string `json:"title,omitempty"`
// Icons for the prompt, if any.
Icons []Icon `json:"icons,omitempty"`
}
// Describes an argument that a prompt can accept.
type PromptArgument struct {
// Intended for programmatic or logical use, but used as a display name in past
// specs or fallback (if title isn't present).
Name string `json:"name"`
// Intended for UI and end-user contexts — optimized to be human-readable and
// easily understood, even by those unfamiliar with domain-specific terminology.
Title string `json:"title,omitempty"`
// A human-readable description of the argument.
Description string `json:"description,omitempty"`
// Whether this argument must be provided.
Required bool `json:"required,omitempty"`
}
type PromptListChangedParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
func (x *PromptListChangedParams) isParams() {}
func (x *PromptListChangedParams) GetProgressToken() any { return getProgressToken(x) }
func (x *PromptListChangedParams) SetProgressToken(t any) { setProgressToken(x, t) }
// 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.
type PromptMessage struct {
Content Content `json:"content"`
Role Role `json:"role"`
}
// UnmarshalJSON handles the unmarshalling of content into the Content
// interface.
func (m *PromptMessage) UnmarshalJSON(data []byte) error {
type msg PromptMessage // avoid recursion
var wire struct {
msg
Content *wireContent `json:"content"`
}
if err := json.Unmarshal(data, &wire); err != nil {
return err
}
var err error
if wire.msg.Content, err = contentFromWire(wire.Content, nil); err != nil {
return err
}
*m = PromptMessage(wire.msg)
return nil
}
type ReadResourceParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The URI of the resource to read. The URI can use any protocol; it is up to
// the server how to interpret it.
URI string `json:"uri"`
}
func (x *ReadResourceParams) isParams() {}
func (x *ReadResourceParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ReadResourceParams) SetProgressToken(t any) { setProgressToken(x, t) }
// The server's response to a resources/read request from the client.
type ReadResourceResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
Contents []*ResourceContents `json:"contents"`
}
func (*ReadResourceResult) isResult() {}
// A known resource that the server is capable of reading.
type Resource struct {
// See [specification/2025-06-18/basic/index#general-fields] for notes on _meta
// usage.
Meta `json:"_meta,omitempty"`
// Optional annotations for the client.
Annotations *Annotations `json:"annotations,omitempty"`
// 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.
Description string `json:"description,omitempty"`
// The MIME type of this resource, if known.
MIMEType string `json:"mimeType,omitempty"`
// Intended for programmatic or logical use, but used as a display name in past
// specs or fallback (if title isn't present).
Name string `json:"name"`
// The size of the raw resource content, in bytes (i.e., before base64 encoding
// or any tokenization), if known.
//
// This can be used by Hosts to display file sizes and estimate context window
// usage.
Size int64 `json:"size,omitempty"`
// Intended for UI and end-user contexts — optimized to be human-readable and
// easily understood, even by those unfamiliar with domain-specific terminology.
//
// If not provided, the name should be used for display (except for Tool, where
// Annotations.Title should be given precedence over using name, if
// present).
Title string `json:"title,omitempty"`
// The URI of this resource.
URI string `json:"uri"`
// Icons for the resource, if any.
Icons []Icon `json:"icons,omitempty"`
}
type ResourceListChangedParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
func (x *ResourceListChangedParams) isParams() {}
func (x *ResourceListChangedParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ResourceListChangedParams) SetProgressToken(t any) { setProgressToken(x, t) }
// A template description for resources available on the server.
type ResourceTemplate struct {
// See [specification/2025-06-18/basic/index#general-fields] for notes on _meta
// usage.
Meta `json:"_meta,omitempty"`
// Optional annotations for the client.
Annotations *Annotations `json:"annotations,omitempty"`
// 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.
Description string `json:"description,omitempty"`
// 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.
MIMEType string `json:"mimeType,omitempty"`
// Intended for programmatic or logical use, but used as a display name in past
// specs or fallback (if title isn't present).
Name string `json:"name"`
// Intended for UI and end-user contexts — optimized to be human-readable and
// easily understood, even by those unfamiliar with domain-specific terminology.
//
// If not provided, the name should be used for display (except for Tool, where
// Annotations.Title should be given precedence over using name, if
// present).
Title string `json:"title,omitempty"`
// A URI template (according to RFC 6570) that can be used to construct resource
// URIs.
URITemplate string `json:"uriTemplate"`
// Icons for the resource template, if any.
Icons []Icon `json:"icons,omitempty"`
}
// The sender or recipient of messages and data in a conversation.
type Role string
// Represents a root directory or file that the server can operate on.
type Root struct {
// See [specification/2025-06-18/basic/index#general-fields] for notes on _meta
// usage.
Meta `json:"_meta,omitempty"`
// 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.
Name string `json:"name,omitempty"`
// 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.
URI string `json:"uri"`
}
type RootsListChangedParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
func (x *RootsListChangedParams) isParams() {}
func (x *RootsListChangedParams) GetProgressToken() any { return getProgressToken(x) }
func (x *RootsListChangedParams) SetProgressToken(t any) { setProgressToken(x, t) }
// TODO: to be consistent with ServerCapabilities, move the capability types
// below directly above ClientCapabilities.
// SamplingCapabilities describes the client's support for sampling.
type SamplingCapabilities struct{}
// ElicitationCapabilities describes the capabilities for elicitation.
//
// If neither Form nor URL is set, the 'Form' capabilitiy is assumed.
type ElicitationCapabilities struct {
Form *FormElicitationCapabilities `json:"form,omitempty"`
URL *URLElicitationCapabilities `json:"url,omitempty"`
}
// FormElicitationCapabilities describes capabilities for form elicitation.
type FormElicitationCapabilities struct {
}
// URLElicitationCapabilities describes capabilities for url elicitation.
type URLElicitationCapabilities struct {
}
// Describes a message issued to or received from an LLM API.
type SamplingMessage struct {
Content Content `json:"content"`
Role Role `json:"role"`
}
// UnmarshalJSON handles the unmarshalling of content into the Content
// interface.
func (m *SamplingMessage) UnmarshalJSON(data []byte) error {
type msg SamplingMessage // avoid recursion
var wire struct {
msg
Content *wireContent `json:"content"`
}
if err := json.Unmarshal(data, &wire); err != nil {
return err
}
var err error
if wire.msg.Content, err = contentFromWire(wire.Content, map[string]bool{"text": true, "image": true, "audio": true}); err != nil {
return err
}
*m = SamplingMessage(wire.msg)
return nil
}
type SetLoggingLevelParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// 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/message.
Level LoggingLevel `json:"level"`
}
func (x *SetLoggingLevelParams) isParams() {}
func (x *SetLoggingLevelParams) GetProgressToken() any { return getProgressToken(x) }
func (x *SetLoggingLevelParams) SetProgressToken(t any) { setProgressToken(x, t) }
// Definition for a tool the client can call.
type Tool struct {
// See [specification/2025-06-18/basic/index#general-fields] for notes on _meta
// usage.
Meta `json:"_meta,omitempty"`
// Optional additional tool information.
//
// Display name precedence order is: title, annotations.title, then name.
Annotations *ToolAnnotations `json:"annotations,omitempty"`
// A human-readable description of the tool.
//
// This can be used by clients to improve the LLM's understanding of available
// tools. It can be thought of like a "hint" to the model.
Description string `json:"description,omitempty"`
// InputSchema holds a JSON Schema object defining the expected parameters
// for the tool.
//
// From the server, this field may be set to any value that JSON-marshals to
// valid JSON schema (including json.RawMessage). However, for tools added
// using [AddTool], which automatically validates inputs and outputs, the
// schema must be in a draft the SDK understands. Currently, the SDK uses
// github.com/google/jsonschema-go for inference and validation, which only
// supports the 2020-12 draft of JSON schema. To do your own validation, use
// [Server.AddTool].
//
// From the client, this field will hold the default JSON marshaling of the
// server's input schema (a map[string]any).
InputSchema any `json:"inputSchema"`
// Intended for programmatic or logical use, but used as a display name in past
// specs or fallback (if title isn't present).
Name string `json:"name"`
// OutputSchema holds an optional JSON Schema object defining the structure
// of the tool's output returned in the StructuredContent field of a
// CallToolResult.
//
// From the server, this field may be set to any value that JSON-marshals to
// valid JSON schema (including json.RawMessage). However, for tools added
// using [AddTool], which automatically validates inputs and outputs, the
// schema must be in a draft the SDK understands. Currently, the SDK uses
// github.com/google/jsonschema-go for inference and validation, which only
// supports the 2020-12 draft of JSON schema. To do your own validation, use
// [Server.AddTool].
//
// From the client, this field will hold the default JSON marshaling of the
// server's output schema (a map[string]any).
OutputSchema any `json:"outputSchema,omitempty"`
// Intended for UI and end-user contexts — optimized to be human-readable and
// easily understood, even by those unfamiliar with domain-specific terminology.
// If not provided, Annotations.Title should be used for display if present,
// otherwise Name.
Title string `json:"title,omitempty"`
// Icons for the tool, if any.
Icons []Icon `json:"icons,omitempty"`
}
// Additional properties describing a Tool to clients.
//
// NOTE: all properties in ToolAnnotations are hints. They are not
// guaranteed to provide a faithful description of tool behavior (including
// descriptive properties like title).
//
// Clients should never make tool use decisions based on ToolAnnotations
// received from untrusted servers.
type ToolAnnotations struct {
// If true, the tool may perform destructive updates to its environment. If
// false, the tool performs only additive updates.
//
// (This property is meaningful only when ReadOnlyHint == false.)
//
// Default: true
DestructiveHint *bool `json:"destructiveHint,omitempty"`
// If true, calling the tool repeatedly with the same arguments will have no
// additional effect on the its environment.
//
// (This property is meaningful only when ReadOnlyHint == false.)
//
// Default: false
IdempotentHint bool `json:"idempotentHint,omitempty"`
// If true, this tool may interact with an "open world" of external entities. If
// false, the tool's domain of interaction is closed. For example, the world of
// a web search tool is open, whereas that of a memory tool is not.
//
// Default: true
OpenWorldHint *bool `json:"openWorldHint,omitempty"`
// If true, the tool does not modify its environment.
//
// Default: false
ReadOnlyHint bool `json:"readOnlyHint,omitempty"`
// A human-readable title for the tool.
Title string `json:"title,omitempty"`
}
type ToolListChangedParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
func (x *ToolListChangedParams) isParams() {}
func (x *ToolListChangedParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ToolListChangedParams) SetProgressToken(t any) { setProgressToken(x, t) }
// Sent from the client to request resources/updated notifications from the
// server whenever a particular resource changes.
type SubscribeParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The URI of the resource to subscribe to.
URI string `json:"uri"`
}
func (*SubscribeParams) isParams() {}
// Sent from the client to request cancellation of resources/updated
// notifications from the server. This should follow a previous
// resources/subscribe request.
type UnsubscribeParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The URI of the resource to unsubscribe from.
URI string `json:"uri"`
}
func (*UnsubscribeParams) isParams() {}
// 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.
type ResourceUpdatedNotificationParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The URI of the resource that has been updated. This might be a sub-resource of the one that the client actually subscribed to.
URI string `json:"uri"`
}
func (*ResourceUpdatedNotificationParams) isParams() {}
// TODO(jba): add CompleteRequest and related types.
// A request from the server to elicit additional information from the user via the client.
type ElicitParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The mode of elicitation to use.
//
// If unset, will be inferred from the other fields.
Mode string `json:"mode"`
// The message to present to the user.
Message string `json:"message"`
// A JSON schema object defining the requested elicitation schema.
//
// From the server, this field may be set to any value that can JSON-marshal
// to valid JSON schema (including json.RawMessage for raw schema values).
// Internally, the SDK uses github.com/google/jsonschema-go for validation,
// which only supports the 2020-12 draft of the JSON schema spec.
//
// From the client, this field will use the default JSON marshaling (a
// map[string]any).
//
// Only top-level properties are allowed, without nesting.
//
// This is only used for "form" elicitation.
RequestedSchema any `json:"requestedSchema,omitempty"`
// The URL to present to the user.
//
// This is only used for "url" elicitation.
URL string `json:"url,omitempty"`
// The ID of the elicitation.
//
// This is only used for "url" elicitation.
ElicitationID string `json:"elicitationId,omitempty"`
}
func (x *ElicitParams) isParams() {}
func (x *ElicitParams) GetProgressToken() any { return getProgressToken(x) }
func (x *ElicitParams) SetProgressToken(t any) { setProgressToken(x, t) }
// The client's response to an elicitation/create request from the server.
type ElicitResult struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The user action in response to the elicitation.
// - "accept": User submitted the form/confirmed the action
// - "decline": User explicitly declined the action
// - "cancel": User dismissed without making an explicit choice
Action string `json:"action"`
// The submitted form data, only present when action is "accept".
// Contains values matching the requested schema.
Content map[string]any `json:"content,omitempty"`
}
func (*ElicitResult) isResult() {}
// ElicitationCompleteParams is sent from the server to the client, informing it that an out-of-band elicitation interaction has completed.
type ElicitationCompleteParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta `json:"_meta,omitempty"`
// The ID of the elicitation that has completed. This must correspond to the
// elicitationId from the original elicitation/create request.
ElicitationID string `json:"elicitationId"`
}
func (*ElicitationCompleteParams) isParams() {}
// An Implementation describes the name and version of an MCP implementation, with an optional
// title for UI representation.
type Implementation struct {
// Intended for programmatic or logical use, but used as a display name in past
// specs or fallback (if title isn't present).
Name string `json:"name"`
// Intended for UI and end-user contexts — optimized to be human-readable and
// easily understood, even by those unfamiliar with domain-specific terminology.
Title string `json:"title,omitempty"`
Version string `json:"version"`
// WebsiteURL for the server, if any.
WebsiteURL string `json:"websiteUrl,omitempty"`
// Icons for the Server, if any.
Icons []Icon `json:"icons,omitempty"`
}
// CompletionCapabilities describes the server's support for argument autocompletion.
type CompletionCapabilities struct{}
// LoggingCapabilities describes the server's support for sending log messages to the client.
type LoggingCapabilities struct{}
// PromptCapabilities describes the server's support for prompts.
type PromptCapabilities struct {
// Whether this server supports notifications for changes to the prompt list.
ListChanged bool `json:"listChanged,omitempty"`
}
// ResourceCapabilities describes the server's support for resources.
type ResourceCapabilities struct {
// ListChanged reports whether the client supports notifications for
// changes to the resource list.
ListChanged bool `json:"listChanged,omitempty"`
// Subscribe reports whether this server supports subscribing to resource
// updates.
Subscribe bool `json:"subscribe,omitempty"`
}
// ToolCapabilities describes the server's support for tools.
type ToolCapabilities struct {
// ListChanged reports whether the client supports notifications for
// changes to the tool list.
ListChanged bool `json:"listChanged,omitempty"`
}
// ServerCapabilities describes capabilities that a server supports.
type ServerCapabilities struct {
// NOTE: any addition to ServerCapabilities must also be reflected in
// [ServerCapabilities.clone].
// Experimental reports non-standard capabilities that the server supports.
Experimental map[string]any `json:"experimental,omitempty"`
// Completions is present if the server supports argument autocompletion
// suggestions.
Completions *CompletionCapabilities `json:"completions,omitempty"`
// Logging is present if the server supports log messages.
Logging *LoggingCapabilities `json:"logging,omitempty"`
// Prompts is present if the server supports prompts.
Prompts *PromptCapabilities `json:"prompts,omitempty"`
// Resources is present if the server supports resourcs.
Resources *ResourceCapabilities `json:"resources,omitempty"`
// Tools is present if the supports tools.
Tools *ToolCapabilities `json:"tools,omitempty"`
}
// clone returns a deep copy of the ServerCapabilities.
func (c *ServerCapabilities) clone() *ServerCapabilities {
cp := *c
cp.Completions = shallowClone(c.Completions)
cp.Logging = shallowClone(c.Logging)
cp.Prompts = shallowClone(c.Prompts)
cp.Resources = shallowClone(c.Resources)
cp.Tools = shallowClone(c.Tools)
return &cp
}
const (
methodCallTool = "tools/call"
notificationCancelled = "notifications/cancelled"
methodComplete = "completion/complete"
methodCreateMessage = "sampling/createMessage"
methodElicit = "elicitation/create"
notificationElicitationComplete = "notifications/elicitation/complete"
methodGetPrompt = "prompts/get"
methodInitialize = "initialize"
notificationInitialized = "notifications/initialized"
methodListPrompts = "prompts/list"
methodListResourceTemplates = "resources/templates/list"
methodListResources = "resources/list"
methodListRoots = "roots/list"
methodListTools = "tools/list"
notificationLoggingMessage = "notifications/message"
methodPing = "ping"
notificationProgress = "notifications/progress"
notificationPromptListChanged = "notifications/prompts/list_changed"
methodReadResource = "resources/read"
notificationResourceListChanged = "notifications/resources/list_changed"
notificationResourceUpdated = "notifications/resources/updated"
notificationRootsListChanged = "notifications/roots/list_changed"
methodSetLevel = "logging/setLevel"
methodSubscribe = "resources/subscribe"
notificationToolListChanged = "notifications/tools/list_changed"
methodUnsubscribe = "resources/unsubscribe"
)