MCP endpoint in LangGraph Server

The Model Context Protocol (MCP) is an open protocol for describing tools and data sources in a model-agnostic format, enabling LLMs to discover and use them via a structured API.

LangGraph Server implements MCP using the Streamable HTTP transport. This allows LangGraph agents to be exposed as MCP tools, making them usable with any MCP-compliant client supporting Streamable HTTP.

The MCP endpoint is available at /mcp on LangGraph Server.

You can set up custom authentication middleware to authenticate a user with an MCP server to get access to user-scoped tools within your LangGraph Platform deployment.

An example architecture for this flow:

Requirements

To use MCP, ensure you have the following dependencies installed:

• langgraph-api >= 0.2.3
• langgraph-sdk >= 0.1.61

Install them with:

pip install "langgraph-api>=0.2.3" "langgraph-sdk>=0.1.61"

Usage overview

To enable MCP:

• Upgrade to use langgraph-api>=0.2.3. If you are deploying LangGraph Platform, this will be done for you automatically if you create a new revision.
• MCP tools (agents) will be automatically exposed.
• Connect with any MCP-compliant client that supports Streamable HTTP.

Client

Use an MCP-compliant client to connect to the LangGraph server. The following examples show how to connect using different programming languages.

JavaScript/TypeScript

npm install @modelcontextprotocol/sdk

Note Replace serverUrl with your LangGraph server URL and configure authentication headers as needed.

import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StreamableHTTPClientTransport } from "@modelcontextprotocol/sdk/client/streamableHttp.js";

// Connects to the LangGraph MCP endpoint
async function connectClient(url) {
    const baseUrl = new URL(url);
    const client = new Client({
        name: 'streamable-http-client',
        version: '1.0.0'
    });

    const transport = new StreamableHTTPClientTransport(baseUrl);
    await client.connect(transport);

    console.log("Connected using Streamable HTTP transport");
    console.log(JSON.stringify(await client.listTools(), null, 2));
    return client;
}

const serverUrl = "http://localhost:2024/mcp";

connectClient(serverUrl)
    .then(() => {
        console.log("Client connected successfully");
    })
    .catch(error => {
        console.error("Failed to connect client:", error);
    });

Expose an agent as MCP tool

When deployed, your agent will appear as a tool in the MCP endpoint with this configuration:

• Tool name: The agent’s name.
• Tool description: The agent’s description.
• Tool input schema: The agent’s input schema.

Setting name and description

You can set the name and description of your agent in langgraph.json:

{
    "graphs": {
        "my_agent": {
            "path": "./my_agent/agent.py:graph",
            "description": "A description of what the agent does"
        }
    },
    "env": ".env"
}

After deployment, you can update the name and description using the LangGraph SDK.

Schema

Define clear, minimal input and output schemas to avoid exposing unnecessary internal complexity to the LLM.

The default MessagesState uses AnyMessage, which supports many message types but is too general for direct LLM exposure.

Instead, define custom agents or workflows that use explicitly typed input and output structures.

For example, a workflow answering documentation questions might look like this:

from langgraph.graph import StateGraph, START, END
from typing_extensions import TypedDict

# Define input schema
class InputState(TypedDict):
    question: str

# Define output schema
class OutputState(TypedDict):
    answer: str

# Combine input and output
class OverallState(InputState, OutputState):
    pass

# Define the processing node
def answer_node(state: InputState):
    # Replace with actual logic and do something useful
    return {"answer": "bye", "question": state["question"]}

# Build the graph with explicit schemas
builder = StateGraph(OverallState, input_schema=InputState, output_schema=OutputState)
builder.add_node(answer_node)
builder.add_edge(START, "answer_node")
builder.add_edge("answer_node", END)
graph = builder.compile()

# Run the graph
print(graph.invoke({"question": "hi"}))

For more details, see the low-level concepts guide.

Use user-scoped MCP tools in your deployment

Prerequisites You have added your own custom auth middleware that populates the langgraph_auth_user object, making it accessible through configurable context for every node in your graph.

To make user-scoped tools available to your LangGraph Platform deployment, start with implementing a snippet like the following:

from langchain_mcp_adapters.client import MultiServerMCPClient

def mcp_tools_node(state, config):
    user = config["configurable"].get("langgraph_auth_user")
         , user["github_token"], user["email"], etc.

    client = MultiServerMCPClient({
        "github": {
            "transport": "streamable_http", # (1)
            "url": "https://my-github-mcp-server/mcp", # (2)
            "headers": {
                "Authorization": f"Bearer {user['github_token']}"
            }
        }
    })
    tools = await client.get_tools() # (3)

    # Your tool-calling logic here

    tool_messages = ...
    return {"messages": tool_messages}

1. MCP only supports adding headers to requests made to streamable_http and sse transport servers.
2. Your MCP server URL.
3. Get available tools from your MCP server.

This can also be done by rebuilding your graph at runtime to have a different configuration for a new run

Session behavior

The current LangGraph MCP implementation does not support sessions. Each /mcp request is stateless and independent.

Authentication

The /mcp endpoint uses the same authentication as the rest of the LangGraph API. Refer to the authentication guide for setup details.

Disable MCP

To disable the MCP endpoint, set disable_mcp to true in your langgraph.json configuration file:

{
  "http": {
    "disable_mcp": true
  }
}

This will prevent the server from exposing the /mcp endpoint.