gRPC Transport for MCP

Warning

Experimental / Proof of Concept

This package is a proof of concept for experimentation purposes. It is not intended for production use. The official Python package is being developed at GoogleCloudPlatform/mcp-grpc-transport-py — please follow/star that repo to stay updated.

A gRPC transport implementation for the Model Context Protocol (MCP) using FastMCP.

Background

• SEP: gRPC as a native MCP transport — the specification enhancement proposal
• Blog: gRPC as a Native Transport for MCP

Features

• Server: expose a FastMCP server over gRPC
• Client: call a gRPC MCP server and get back native mcp.types objects
• Tool calls with text and image content, structured output, and progress reporting
• Proto definitions sourced from GoogleCloudPlatform/mcp-grpc-transport-proto

Installation

uv sync

The proto package (mcp-transport-proto) is fetched directly from GitHub via [tool.uv.sources] — no manual proto compilation needed.

Server

import asyncio
from mcp.server.fastmcp import FastMCP
from grpcmcp import serve_grpc

mcp = FastMCP("My Server")

@mcp.tool()
async def my_tool(x: int) -> str:
    """Does something useful."""
    return str(x)

if __name__ == "__main__":
    asyncio.run(serve_grpc(mcp))          # default: 0.0.0.0:50051
    # asyncio.run(serve_grpc(mcp, port=9090))

Client

import asyncio
from grpcmcp import GRPCClient

async def main():
    async with GRPCClient("localhost", 50051) as client:
        tools = await client.list_tools()
        for tool in tools.tools:
            print(f"{tool.name}: {tool.description}")

        result = await client.call_tool("my_tool", {"x": 42})
        for content in result.content:
            if content.type == "text":
                print(content.text)

asyncio.run(main())

GRPCClient reference

Parameter	Type	Description
host	str	Server hostname
port	int	Server port
timeout	float | None	Default per-call timeout in seconds
channel_options	list[tuple] | None	Raw gRPC channel options

Method	Returns
list_tools()	types.ListToolsResult
call_tool(name, arguments)	types.CallToolResult

Running the examples

Start the server:

uv run python example/grpc_example_server.py

In another terminal, run the client:

uv run python example/grpc_example_client.py

Requirements

• Python >= 3.10
• grpcio >= 1.78.0
• protobuf >= 4.25.0
• mcp == 1.25.0