LangChain (TypeScript) MCP server

This client provides integration between LangChain.js and the Model Context Protocol (MCP), allowing you to incorporate MCP capabilities into your LangChain-based applications. It serves as a JavaScript/TypeScript port of the Python-based langchain-mcp client.

Installation

The MCP LangChain client can be installed using npm:

npm install mcp-langchain-ts-client

Usage

Basic Setup

To use the MCP LangChain client, you'll need to initialize the toolkit with server parameters and then extract the LangChain-compatible tools:

const serverParams = {
  command: "npx",
  args: [
    "-y",
    "@modelcontextprotocol/server-everything"
  ]
}

// Initialize the toolkit
const toolkit = new MCPToolkit(serverParams);
await toolkit.initialize();

// Extract LangChain.js compatible tools
const tools = toolkit.tools;

Using with LangChain Agents

Once you have the tools, you can use them with LangChain agents. Here's an example using the ReAct agent with Claude:

import { createReactAgent } from "@langchain/langgraph/prebuilt";
import { ChatAnthropic } from "@langchain/anthropic";

const llm = new ChatAnthropic({ model: 'claude-3-5-sonnet-20241022' });
const agent = createReactAgent({ llm, tools });

Server Configuration

The serverParams object configures how the MCP server is launched:

const serverParams = {
  command: "npx", // The command to run
  args: [         // Arguments for the command
    "-y",
    "@modelcontextprotocol/server-everything"
  ]
}

This configuration uses npx to launch the MCP server package without permanently installing it.

How to install this MCP server

For Claude Code

To add this MCP server to Claude Code, run this command in your terminal:

claude mcp add-json "mcp-langchain-ts-client" '{"command":"npx","args":["-y","@modelcontextprotocol/server-everything"]}'

See the official Claude Code MCP documentation for more details.

For Cursor

There are two ways to add an MCP server to Cursor. The most common way is to add the server globally in the ~/.cursor/mcp.json file so that it is available in all of your projects.

If you only need the server in a single project, you can add it to the project instead by creating or adding it to the .cursor/mcp.json file.

Adding an MCP server to Cursor globally

To add a global MCP server go to Cursor Settings > Tools & Integrations and click "New MCP Server".

When you click that button the ~/.cursor/mcp.json file will be opened and you can add your server like this:

{
    "mcpServers": {
        "mcp-langchain-ts-client": {
            "command": "npx",
            "args": [
                "-y",
                "@modelcontextprotocol/server-everything"
            ]
        }
    }
}

Adding an MCP server to a project

To add an MCP server to a project you can create a new .cursor/mcp.json file or add it to the existing one. This will look exactly the same as the global MCP server example above.

How to use the MCP server

Once the server is installed, you might need to head back to Settings > MCP and click the refresh button.

The Cursor agent will then be able to see the available tools the added MCP server has available and will call them when it needs to.

You can also explicitly ask the agent to use the tool by mentioning the tool name and describing what the function does.

For Claude Desktop

To add this MCP server to Claude Desktop:

1. Find your configuration file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json
• Linux: ~/.config/Claude/claude_desktop_config.json

2. Add this to your configuration file:

{
    "mcpServers": {
        "mcp-langchain-ts-client": {
            "command": "npx",
            "args": [
                "-y",
                "@modelcontextprotocol/server-everything"
            ]
        }
    }
}

3. Restart Claude Desktop for the changes to take effect