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MCP Integration

Model Context Protocol (MCP) is an open protocol that standardizes how applications provide tools and context to language models. LangGraph agents can use tools defined on MCP servers through the langchain-mcp-adapters library.

MCP

Install the langchain-mcp-adapters library to use MCP tools in LangGraph:

pip install langchain-mcp-adapters

Use MCP tools

The langchain-mcp-adapters package enables agents to use tools defined across one or more MCP servers.

Agent using tools defined on MCP servers
from langchain_mcp_adapters.client import MultiServerMCPClient
from langgraph.prebuilt import create_react_agent

async with MultiServerMCPClient(
    {
        "math": {
            "command": "python",
            # Replace with absolute path to your math_server.py file
            "args": ["/path/to/math_server.py"],
            "transport": "stdio",
        },
        "weather": {
            # Ensure your start your weather server on port 8000
            "url": "http://localhost:8000/sse",
            "transport": "sse",
        }
    }
) as client:
    agent = create_react_agent(
        "anthropic:claude-3-7-sonnet-latest",
        client.get_tools()
    )
    math_response = await agent.ainvoke({"messages": "what's (3 + 5) x 12?"})
    weather_response = await agent.ainvoke({"messages": "what is the weather in nyc?"})

Custom MCP servers

To create your own MCP servers, you can use the mcp library. This library provides a simple way to define tools and run them as servers.

Install the MCP library:

pip install mcp
Use the following reference implementations to test your agent with MCP tool servers.

Example Math Server (stdio transport)
from mcp.server.fastmcp import FastMCP

mcp = FastMCP("Math")

@mcp.tool()
def add(a: int, b: int) -> int:
    """Add two numbers"""
    return a + b

@mcp.tool()
def multiply(a: int, b: int) -> int:
    """Multiply two numbers"""
    return a * b

if __name__ == "__main__":
    mcp.run(transport="stdio")
Example Weather Server (SSE transport)
from mcp.server.fastmcp import FastMCP

mcp = FastMCP("Weather")

@mcp.tool()
async def get_weather(location: str) -> str:
    """Get weather for location."""
    return "It's always sunny in New York"

if __name__ == "__main__":
    mcp.run(transport="sse")

Additional resources

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