elixir-mcp-server

Model Context Protocol (MCP) server framework for Elixir/BEAM

A complete, production-ready implementation of the Model Context Protocol that enables Elixir applications to integrate with Claude Code and other MCP clients.

Features

• ✅ Complete JSON-RPC 2.0 protocol implementation

• ✅ stdio transport (MCP standard)

• ✅ Tool registration and execution

• ✅ Resource serving (planned)

• ✅ Prompt templates (planned)

• ✅ Server capabilities negotiation

• ✅ Type-safe tool definitions via behaviors

• ✅ OTP supervision for reliability

Installation

Add elixir_mcp_server to your mix.exs dependencies:

def deps do
  [
    {:elixir_mcp_server, "~> 0.1.0"}
  ]
end

Quick Start

Define a Tool

defmodule MyApp.Tools.Echo do
  use ElixirMcpServer.Tool

  @impl true
  def name, do: "echo"

  @impl true
  def description, do: "Echoes back the input message"

  @impl true
  def input_schema do
    %{
      type: "object",
      properties: %{
        message: %{type: "string", description: "Message to echo"}
      },
      required: ["message"]
    }
  end

  @impl true
  def execute(%{"message" => msg}, _context) do
    {:ok, [%{type: "text", text: "Echo: #{msg}"}]}
  end
end

Start the Server

ElixirMcpServer.start_link(
  name: "my-app",
  version: "1.0.0",
  tools: [MyApp.Tools.Echo]
)

Configure Claude Code

Add to your .claude.json:

{
  "mcpServers": {
    "my-app": {
      "command": "mix",
      "args": ["run", "--no-halt"],
      "env": {}
    }
  }
}

Use Cases

This framework is useful for:

• feedback-o-tron - Automated feedback submission with network verification

• Observatory - GitHub intelligence and issue management

• NeuroPhone - Elixir/Phoenix applications

• Any Elixir service that wants Claude Code integration

Architecture

┌─────────────────────────────────────┐
│   MCP Client (Claude Code, etc.)    │
└─────────────────┬───────────────────┘
                  │ JSON-RPC 2.0 / stdio
┌─────────────────▼───────────────────┐
│    ElixirMcpServer.Server           │
│    (GenServer, protocol handling)   │
└─────────────────┬───────────────────┘
                  │
    ┌─────────────┼─────────────┐
    │             │             │
┌───▼───┐    ┌───▼────┐   ┌───▼──────┐
│ Tools │    │Resources│   │ Prompts  │
│(your) │    │ (your)  │   │  (your)  │
└───────┘    └─────────┘   └──────────┘

Documentation

• API Documentation

• Changelog

• Security Policy

License

PMPL-1.0-or-later - see LICENSE file for details

OPSM Link

OPSM Core
  |
  v
elixir-mcp-server (Elixir tooling bridge for OPSM)