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internal/mcp: meta and progress token

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Meta is a struct that contains a map[string]any, and a ProgressToken
field.

Each Params and Result type has a Meta as a value field.

Meta marshals and unmarshals specially, so the ProgressToken field
becomes part of the map. The marshalling code is generalized in
anticipation of every Params and Result growing a map of additional
properties.

Change-Id: I6d2f34270d33501c96437f24f91ef3e51d20d955
Reviewed-on: https://go-review.googlesource.com/c/tools/+/674956
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Jonathan Amsterdam 2025-05-21 07:11:50 -04:00 • committed by Gopher Robot
commit 7130f0f081
1 changed files with 548 additions and 115 deletions
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201
mcp/protocol.go
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@ -29,10 +29,15 @@ type Annotations struct {
}
type CallToolParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
Arguments json.RawMessage `json:"arguments,omitempty"`
Name string `json:"name"`
}
func (x *CallToolParams) GetMeta() *Meta { return &x.Meta }
// The server's response to a tool call.
//
// Any errors that originate from the tool SHOULD be reported inside the result
@ -44,17 +49,22 @@ type CallToolParams struct {
// server does not support tool calls, or any other exceptional conditions,
// should be reported as an MCP error response.
type CallToolResult struct {
// This result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
Content []*Content `json:"content"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
Content []*Content `json:"content"`
// Whether the tool call ended in an error.
//
// If not set, this is assumed to be false (the call was successful).
IsError bool `json:"isError,omitempty"`
}
func (x *CallToolResult) GetMeta() *Meta { return &x.Meta }
type CancelledParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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"`
@ -65,6 +75,8 @@ type CancelledParams struct {
RequestID any `json:"requestId"`
}
func (x *CancelledParams) GetMeta() *Meta { return &x.Meta }
// 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.
@ -82,6 +94,9 @@ type ClientCapabilities struct {
}
type CreateMessageParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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"`
@ -103,15 +118,17 @@ type CreateMessageParams struct {
Temperature float64 `json:"temperature,omitempty"`
}
func (x *CreateMessageParams) GetMeta() *Meta { return &x.Meta }
// 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 result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
Content *Content `json:"content"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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"`
@ -119,24 +136,36 @@ type CreateMessageResult struct {
StopReason string `json:"stopReason,omitempty"`
}
func (x *CreateMessageResult) GetMeta() *Meta { return &x.Meta }
type GetPromptParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
// The server's response to a prompts/get request from the client.
type GetPromptResult struct {
// This result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
// An optional description for the prompt.
Description string `json:"description,omitempty"`
Messages []*PromptMessage `json:"messages"`
}
func (x *GetPromptResult) GetMeta() *Meta { return &x.Meta }
type InitializeParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
Capabilities *ClientCapabilities `json:"capabilities"`
ClientInfo *implementation `json:"clientInfo"`
// The latest version of the Model Context Protocol that the client supports.
@ -144,13 +173,15 @@ type InitializeParams struct {
ProtocolVersion string `json:"protocolVersion"`
}
func (x *InitializeParams) GetMeta() *Meta { return &x.Meta }
// After receiving an initialize request from the client, the server sends this
// response.
type InitializeResult struct {
// This result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
Capabilities *serverCapabilities `json:"capabilities"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
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
@ -164,83 +195,108 @@ type InitializeResult struct {
ServerInfo *implementation `json:"serverInfo"`
}
func (x *InitializeResult) GetMeta() *Meta { return &x.Meta }
type InitializedParams struct {
// This parameter name is reserved by MCP to allow clients and servers to attach
// additional metadata to their notifications.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
}
func (x *InitializedParams) GetMeta() *Meta { return &x.Meta }
type ListPromptsParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
// The server's response to a prompts/list request from the client.
type ListPromptsResult struct {
// This result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
type ListResourcesParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
// The server's response to a resources/list request from the client.
type ListResourcesResult struct {
// This result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
type ListRootsParams struct {
Meta struct {
// 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.
ProgressToken any `json:"progressToken,omitempty"`
} `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
}
func (x *ListRootsParams) GetMeta() *Meta { return &x.Meta }
// 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 result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
Roots []*Root `json:"roots"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
Roots []*Root `json:"roots"`
}
func (x *ListRootsResult) GetMeta() *Meta { return &x.Meta }
type ListToolsParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
// The server's response to a tools/list request from the client.
type ListToolsResult struct {
// This result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
// The severity of a log message.
//
// These map to syslog message severities, as specified in RFC-5424:
@ -248,6 +304,9 @@ type ListToolsResult struct {
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 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"`
@ -257,6 +316,8 @@ type LoggingMessageParams struct {
Logger string `json:"logger,omitempty"`
}
func (x *LoggingMessageParams) GetMeta() *Meta { return &x.Meta }
// Hints to use for model selection.
//
// Keys not declared here are currently left unspecified by the spec and are up
@ -310,15 +371,13 @@ type ModelPreferences struct {
}
type PingParams struct {
Meta struct {
// 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.
ProgressToken any `json:"progressToken,omitempty"`
} `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
}
func (x *PingParams) GetMeta() *Meta { return &x.Meta }
// A prompt or prompt template that the server offers.
type Prompt struct {
// A list of arguments to use for templating the prompt.
@ -340,11 +399,13 @@ type PromptArgument struct {
}
type PromptListChangedParams struct {
// This parameter name is reserved by MCP to allow clients and servers to attach
// additional metadata to their notifications.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
}
func (x *PromptListChangedParams) GetMeta() *Meta { return &x.Meta }
// Describes a message returned as part of a prompt.
//
// This is similar to `SamplingMessage`, but also supports the embedding of
@ -355,19 +416,26 @@ type PromptMessage struct {
}
type ReadResourceParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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) GetMeta() *Meta { return &x.Meta }
// The server's response to a resources/read request from the client.
type ReadResourceResult struct {
// This result property is reserved by the protocol to allow clients and servers
// to attach additional metadata to their responses.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
Contents *ResourceContents `json:"contents"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
Contents *ResourceContents `json:"contents"`
}
func (x *ReadResourceResult) GetMeta() *Meta { return &x.Meta }
// A known resource that the server is capable of reading.
type Resource struct {
// Optional annotations for the client.
@ -394,11 +462,13 @@ type Resource struct {
}
type ResourceListChangedParams struct {
// This parameter name is reserved by MCP to allow clients and servers to attach
// additional metadata to their notifications.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
}
func (x *ResourceListChangedParams) GetMeta() *Meta { return &x.Meta }
// The sender or recipient of messages and data in a conversation.
type Role string
@ -415,11 +485,13 @@ type Root struct {
}
type RootsListChangedParams struct {
// This parameter name is reserved by MCP to allow clients and servers to attach
// additional metadata to their notifications.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
}
func (x *RootsListChangedParams) GetMeta() *Meta { return &x.Meta }
// Present if the client supports sampling from an LLM.
type SamplingCapabilities struct {
}
@ -431,12 +503,17 @@ type SamplingMessage struct {
}
type SetLevelParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta 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 *SetLevelParams) GetMeta() *Meta { return &x.Meta }
// Definition for a tool the client can call.
type Tool struct {
// Optional additional tool information.
@ -490,11 +567,13 @@ type ToolAnnotations struct {
}
type ToolListChangedParams struct {
// This parameter name is reserved by MCP to allow clients and servers to attach
// additional metadata to their notifications.
Meta map[string]json.RawMessage `json:"_meta,omitempty"`
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
Meta Meta `json:"_meta,omitempty"`
}
func (x *ToolListChangedParams) GetMeta() *Meta { return &x.Meta }
// Describes the name and version of an MCP implementation.
type implementation struct {
Name string `json:"name"`