modelcontextprotocol/go-sdk
Watch
1
0
Fork
You've already forked go-sdk
 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions 1

mcp: fix broken client root capabilities (#698)

Browse source 
To address #607, add ClientCapabilities.RootsV2, and populate it when
constructing sending and receiving InitializeParams.

Fixes #607
This commit is contained in:
Robert Findley 2025-12-11 10:16:56 -05:00 • committed by GitHub
commit a5e369ed12
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
1 changed files with 288 additions and 57 deletions
Download patch file Download diff file Expand all files Collapse all files

152
mcp/protocol.go
View file

@ -177,23 +177,62 @@ 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 {
// Experimental, non-standard capabilities that the client supports.
// Experimental reports non-standard capabilities that the client supports.
Experimental map[string]any `json:"experimental,omitempty"`
// Present if the client supports listing roots.
// 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 {
// Whether the client supports notifications for changes to the roots list.
// ListChanged reports whether the client supports notifications for
// changes to the roots list.
ListChanged bool `json:"listChanged,omitempty"`
} `json:"roots,omitempty"`
// Present if the client supports sampling from an LLM.
// RootsV2 is present if the client supports roots.
RootsV2 *RootCapabilities `json:"-"`
// Sampling is present if the client supports sampling from an LLM.
Sampling *SamplingCapabilities `json:"sampling,omitempty"`
// Present if the client supports elicitation from the server.
// Elicitation is present if the client supports elicitation from the server.
Elicitation *ElicitationCapabilities `json:"elicitation,omitempty"`
}
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"`
@ -373,27 +412,53 @@ type GetPromptResult struct {
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"`
Meta `json:"_meta,omitempty"`
// Capabilities describes the client's capabilities.
Capabilities *ClientCapabilities `json:"capabilities"`
ClientInfo *Implementation `json:"clientInfo"`
// The latest version of the Model Context Protocol that the client supports.
// The client may decide to support older versions as well.
// 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) }
// After receiving an initialize request from the client, the server sends this
// response.
// 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"`
Meta `json:"_meta,omitempty"`
// Capabilities describes the server's capabilities.
Capabilities *ServerCapabilities `json:"capabilities"`
// Instructions describing how to use the server and its features.
//
@ -411,8 +476,8 @@ type InitializeResult struct {
func (*InitializeResult) isResult() {}
type InitializedParams struct {
// This property is reserved by the protocol to allow clients and servers to
// attach additional metadata to their responses.
// Meta is reserved by the protocol to allow clients and servers to attach
// additional metadata to their responses.
Meta `json:"_meta,omitempty"`
}
@ -875,7 +940,10 @@ func (x *RootsListChangedParams) isParams() {}
func (x *RootsListChangedParams) GetProgressToken() any { return getProgressToken(x) }
func (x *RootsListChangedParams) SetProgressToken(t any) { setProgressToken(x, t) }
// SamplingCapabilities describes the capabilities for sampling.
// 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.
@ -1160,48 +1228,50 @@ type Implementation struct {
Icons []Icon `json:"icons,omitempty"`
}
// Present if the server supports argument autocompletion suggestions.
// CompletionCapabilities describes the server's support for argument autocompletion.
type CompletionCapabilities struct{}
// Present if the server supports sending log messages to the client.
// LoggingCapabilities describes the server's support for sending log messages to the client.
type LoggingCapabilities struct{}
// Present if the server offers any prompt templates.
// 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"`
}
// Present if the server offers any resources to read.
// ResourceCapabilities describes the server's support for resources.
type ResourceCapabilities struct {
// Whether this server supports notifications for changes to the resource list.
// ListChanged reports whether the client supports notifications for
// changes to the resource list.
ListChanged bool `json:"listChanged,omitempty"`
// Whether this server supports subscribing to resource updates.
// Subscribe reports whether this server supports subscribing to resource
// updates.
Subscribe bool `json:"subscribe,omitempty"`
}
// 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.
type ServerCapabilities struct {
// Present if the server supports argument autocompletion suggestions.
Completions *CompletionCapabilities `json:"completions,omitempty"`
// Experimental, non-standard capabilities that the server supports.
Experimental map[string]any `json:"experimental,omitempty"`
// Present if the server supports sending log messages to the client.
Logging *LoggingCapabilities `json:"logging,omitempty"`
// Present if the server offers any prompt templates.
Prompts *PromptCapabilities `json:"prompts,omitempty"`
// Present if the server offers any resources to read.
Resources *ResourceCapabilities `json:"resources,omitempty"`
// Present if the server offers any tools to call.
Tools *ToolCapabilities `json:"tools,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"`
}
// Present if the server offers any tools to call.
type ToolCapabilities struct {
// Whether this server supports notifications for changes to the tool list.
ListChanged bool `json:"listChanged,omitempty"`
// ServerCapabilities describes capabilities that a server supports.
type ServerCapabilities struct {
// 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"`
}
const (