fix: add completion to server capabilities

Author: lariel-fernandes

mcp/types.go

@@ -467,6 +467,8 @@ type ServerCapabilities struct {
 	Experimental map[string]any `json:"experimental,omitempty"`
 	// Present if the server supports sending log messages to the client.
 	Logging *struct{} `json:"logging,omitempty"`
+	// Present if the server supports autocompletion for prompt and resource template arguments.
+	Completion *struct{} `json:"completion,omitempty"`
 	// Present if the server offers any prompt templates.
 	Prompts *struct {
 		// Whether this server supports notifications for changes to the prompt list.

server/server.go

@@ -589,6 +589,10 @@ func (s *MCPServer) handleInitialize(
 		capabilities.Logging = &struct{}{}
 	}
 
+	if s.capabilities.completions != nil && *s.capabilities.completions {
+		capabilities.Completion = &struct{}{}
+	}
+
 	result := mcp.InitializeResult{
 		ProtocolVersion: s.protocolVersion(request.Params.ProtocolVersion),
 		ServerInfo: mcp.Implementation{