Simple MCP Client Using LangChain / Python

This simple Model Context Protocol (MCP) client demonstrates the use of MCP server tools by LangChain ReAct Agent.

It leverages a utility function convert_mcp_to_langchain_tools() from langchain_mcp_tools.
This function handles parallel initialization of specified multiple MCP servers and converts their available tools into a list of LangChain-compatible tools (List[BaseTool]).

Anthropic's claude-3-5-haiku-latest is used as the LLM.
For convenience, code for OpenAI's gpt-4o-mini is also included and commented out.

A bit more realistic (conversational) MCP Client is available here

A typescript equivalent of this MCP client is available here

Prerequisites

• Python 3.11+
• [optional] uv (uvx) installed to run Python package-based MCP servers
• [optional] npm 7+ (npx) to run Node.js package-based MCP servers
• API key from Anthropic (or OpenAI)

Usage

1. Install dependencies:

   make install

2. Setup API key:

   cp .env.template .env

   • Update .env as needed.
   • .gitignore is configured to ignore .env to prevent accidental commits of the credentials.

3. Run the app:

make start

It takes a while on the first run.