Elixir MCP Server

Overview

The Elixir MCP Server is a lightweight, production‑ready implementation of the Model Context Protocol (MCP) that lets AI assistants like Claude interact securely with local and remote resources. By exposing a set of tools over Server‑Sent Events (SSE), the server gives models instant, typed access to filesystem operations and external APIs—here demonstrated with a weather service. This approach removes the need for custom adapters or webhooks, allowing developers to plug the server into any MCP‑compatible workflow with minimal friction.

At its core, the server listens on two endpoints: an SSE stream for real‑time communication and a message endpoint that accepts tool calls. The SSE transport ensures low‑latency, unidirectional updates from the server to the model, while the message endpoint handles inbound tool requests. The implementation uses Elixir’s Bandit and Plug libraries, guaranteeing robust concurrency, fault tolerance, and easy scaling on the BEAM VM.

Key capabilities include:

• File system access – The tool lets models enumerate directory contents, enabling dynamic script generation or data ingestion.
• Echo service – provides a simple round‑trip test, useful for diagnostics or keep‑alive checks.
• Weather lookup – pulls current conditions from WeatherAPI, illustrating how the server can wrap external APIs into a single, well‑defined tool.
• Extensibility – Adding new tools is straightforward: extend the function with tool definitions and implement corresponding clauses.

Developers benefit from the server’s declarative tool definitions, which automatically generate MCP manifests that AI assistants can read. This eliminates manual schema creation and guarantees type safety across the client‑server boundary. Moreover, because the server runs locally, sensitive data never leaves the host machine unless explicitly exposed through a tool.

Typical use cases include:

• Automated data pipelines – A model can read configuration files, trigger scripts, and report results back through the same channel.
• Real‑time monitoring – The server can expose metrics or logs as tools, allowing assistants to query system health on demand.
• API integration – Wrapping any REST or GraphQL endpoint into a tool enables AI‑driven exploration and manipulation of third‑party services without bespoke code.

By leveraging MCP’s standardized transport and tool contract, the Elixir MCP Server empowers developers to build secure, maintainable AI workflows that stay tightly coupled with their existing infrastructure.