grpcmcp

A simple MCP server that will proxy to a grpc backend based on a provided descriptors file or using reflection.

Quick Start

1. Install the binary: go install . or go install github.com/adiom-data/grpcmcp Ensure the go bin directory is in your PATH.

2. In a terminal, run the example grpc server go run example/main.go. This will start a grpc health service on port 8090 with server reflection enabled. Note that this runs on the default port that grpcmcp will connect to.

3. SSE Transport In another terminal, run grpcmcp --hostport=localhost:3000 --reflect. Specifying hostport will use SSE. The SSE endpoint will be served at http://localhost:3000/sse.

4. STDIN Transport Set up the MCP config. e.g.

"grpcmcp": {
    "command": "grpcmcp",
    "args": ["--reflect"]
}

Options / Features

grpcmcp --help for a full list of options.

• hostport string - When set, use SSE, and this serves as the server host:port.

• descriptors string - Specify file location of the protobuf definitions generated from buf build -o protos.pb or protoc --descriptor_set_out=protos.pb instead of using gRPC reflection.

• reflect - If set, use reflection to retrieve gRPC endpoints instead of descriptor file.

• url string - Specify the url of the backend server.

• services string - Comma separated list of fully qualified gRPC service names to filter.

• bearer string - Token to attach in an Authorization: Bearer header.

• bearer-env string - Environment variable for token to attach in an Authorization: Bearer header. Overrides bearer.

• header string (repeatable) - Headers to add in Key: Value format.

• short-names - Use short tool names (ServiceName__MethodName instead of full package path). Falls back to the full path if two services share the same simple name.

• very-short-names - Use very short tool names (MethodName only, no service prefix). Falls back to ServiceName__MethodName if method names collide across services, and to the full path if service names also collide.

• require-method-option string - Only expose methods where a specific proto method option matches a given value. Format: fieldNumber:value (e.g. 50003:1). This filters gRPC methods by checking the raw proto extension field on the method descriptor, so no generated code for the option is needed.

Help

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