LangChain Weather Agent

A simple weather MCP server connected to a LangGraph agent. The agent calls the weather tool to fetch live weather for any city.

Setup

1. Install dependencies:

pip install -r requirements.txt

2. Create a .env file in the project root:

OPENROUTER_API_KEY=your_api_key_here

Usage

Start the MCP server (runs on http://127.0.0.1:8000):

python weatherserver.py

In a second terminal, run the agent client:

python client.py

The client connects to the weather MCP server, loads the weather tool, and asks the LLM about the weather.

Files

File	Description
weatherserver.py	MCP server with a weather tool (geocoding + Open-Meteo API)
client.py	LangGraph agent that uses the MCP weather tool
requirements.txt	Python dependencies

How it works

1. User asks a question like "what's the weather in Tokyo?"
2. The agent calls the weather MCP tool
3. The server geocodes the city name and fetches current weather from Open-Meteo
4. The agent returns the result to the user