Practical MCP with FastMCP & LangChain

Connecting MCP to LangChain

LangChain does not understand MCP natively, but the official langchain-mcp-adapters package bridges the gap. It converts MCP tools into LangChain BaseTool instances so they can be passed directly to create_agent or any other LangChain component.

The adapter's main class is MultiServerMCPClient. You give it a dictionary of server connections and it takes care of establishing sessions, converting schemas, and routing tool calls.

from langchain_mcp_adapters.client import MultiServerMCPClient

client = MultiServerMCPClient(
    {
        # STDIO server: started as a subprocess
        "netflix": {
            "command": "python",
            "args": ["server/main.py"],
            "transport": "stdio",
        },
        # HTTP server: already running, connect by URL
        "netflix_http": {