Add proto2mcp to global extension registry (1179-1181)

[brucearctor]

Extension Registration Request

Project: proto2mcp
Website: https://github.com/protocgen/proto2mcp
Requested Extensions: 1179-1181

About proto2mcp

proto2mcp is a protoc/buf plugin that generates MCP (Model Context Protocol) servers from Protobuf service definitions. It enables existing gRPC/ConnectRPC services to be securely exposed as LLM tools with:

• Automatic JSON Schema generation from proto messages
• Multitenancy support via interceptor middleware
• buf.validate constraint mapping for LLM input validation
• ConnectRPC client forwarding

Extension Usage

proto2mcp uses custom options on three descriptor types:

Extension	Number	Purpose
google.protobuf.MethodOptions	1179	Per-method MCP tool configuration (name override, description, skip, hints)
google.protobuf.ServiceOptions	1180	Per-service MCP configuration (tool name prefix, description)
google.protobuf.FileOptions	1181	Per-file MCP configuration (skip entire file)

Example

import "protocgen/mcp/v1/options.proto";

service PatientService {
  option (protocgen.mcp.v1.service) = {
    tool_name_prefix: "Patient"
    description: "Patient management operations"
  };

  rpc GetPatient(GetPatientRequest) returns (GetPatientResponse) {
    option (protocgen.mcp.v1.method) = {
      description: "Retrieves a patient record by ID"
      read_only: true
    };
  }
}

Related

proto2mcp is part of the protocgen ecosystem, alongside proto2type.