Elixir MCP Server

What is Elixir MCP Server?

An Elixir implementation of the Model Context Protocol (MCP) server using Elixir with Bandit and Plug. It uses SSE (Server-Sent Events) as the transport protocol and provides example tools for AI models to interact with local and remote resources.

How to use Elixir MCP Server?

Install dependencies with mix deps.get, then start the server with the WEATHER_API_KEY environment variable set: WEATHER_API_KEY="your_key" mix run --no-halt. The server is available at http://localhost:4000/sse for SSE and http://localhost:4000/message for messages.

Key features of Elixir MCP Server

• Implements the Model Context Protocol (MCP) using SSE transport
• Built with Elixir, Bandit, and Plug
• Provides three built-in tools: list_files, echo, get_weather
• Supports custom tools by modifying handle_initialize and handle_call_tool
• Can be tested with the NXP Inspector client

Use cases of Elixir MCP Server

• Integrate AI models with local file systems via the list_files tool
• Create echo or debugging endpoints for AI interactions
• Fetch weather data using the get_weather tool and a free WeatherAPI key
• Build custom MCP servers by extending the provided example

FAQ from Elixir MCP Server

What are the runtime requirements?

Elixir 1.18 or higher and Erlang/OTP 27 or higher are required.

How is the server transport configured?

The server uses Server-Sent Events (SSE) as the transport protocol. The SSE endpoint is at /sse and the message endpoint is at /message.

Where does the weather API key come from?

The WEATHER_API_KEY environment variable should hold your API key from the free tier of https://www.weatherapi.com/.

How can I test the server?

Use the NXP Inspector client with SSE transport to list tools, call them, and send ping/keepalive requests.

Can I add my own tools?

Yes. Update the handle_initialize/2 function to define new tools and implement corresponding handle_call_tool/3 clauses.