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mcp: update return meta in DiscoverResult (SEP-2575) (#1097)

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This PR implements the latest changes introduced by
https://github.com/modelcontextprotocol/modelcontextprotocol/pull/3002
This commit is contained in:
Guglielmo Colombo 2026-07-16 16:10:12 +02:00 • committed by GitHub
commit 5cb8339210
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1 changed files with 210 additions and 68 deletions
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38
mcp/server.go
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@ -888,17 +888,21 @@ func (s *Server) discover(_ context.Context, req *ServerRequest[*DiscoverParams]
if versions == nil {
versions = slices.Clone(supportedProtocolVersions)
}
// Read the request-scoped identity/capabilities before acquiring the
// session lock: these accessors may fall back to Session.InitializeParams
// (which also locks Session.mu), so calling them from inside updateState
// would self-deadlock.
init := &InitializeParams{
ProtocolVersion: req.ProtocolVersion(),
Capabilities: req.ClientCapabilities(),
ClientInfo: req.ClientInfo(),
}
req.Session.updateState(func(state *ServerSessionState) {
state.InitializeParams = &InitializeParams{
ProtocolVersion: req.ProtocolVersion(),
Capabilities: req.ClientCapabilities(),
ClientInfo: req.ClientInfo(),
}
state.InitializeParams = init
})
res := &DiscoverResult{
SupportedVersions: versions,
Capabilities: s.capabilities(),
ServerInfo: s.impl,
Instructions: s.opts.Instructions,
}
res.setDefaultCacheableValues()
@ -1924,10 +1928,32 @@ func (ss *ServerSession) handle(ctx context.Context, req *jsonrpc.Request) (any,
}
if validatedMeta.usesNewProtocol {
setCompleteResultType(res)
annotateServerInfo(res, ss.server.impl)
}
return res, nil
}
// annotateServerInfo sets [MetaKeyServerInfo] on the result's `_meta` unless
// it is already present. Per SEP-2575, servers should identify themselves in
// each result's `_meta`.
func annotateServerInfo(res Result, impl *Implementation) {
if res == nil || impl == nil {
return
}
if _, isEmpty := res.(*emptyResult); isEmpty {
return
}
m := res.GetMeta()
if m == nil {
m = map[string]any{}
}
if _, ok := m[MetaKeyServerInfo]; ok {
return
}
m[MetaKeyServerInfo] = impl
res.SetMeta(m)
}
// InitializeParams returns the InitializeParams provided during the client's
// initial connection.
func (ss *ServerSession) InitializeParams() *InitializeParams {