Raxol MCP

MCP (Model Context Protocol) server and client for Elixir. JSON-RPC 2.0 protocol, tool/resource registry, stdio and SSE transports. Build a TUI app, get an AI interface for free.

Install

{:raxol_mcp, "~> 2.4"}

Features

• MCP Server -- GenServer routing tool/resource requests via JSON-RPC 2.0
• MCP Client -- stdio JSON-RPC 2.0 client for consuming external MCP servers
• Registry -- ETS-backed tool/resource/prompt registration (no GenServer bottleneck)
• Transports -- stdio (CLI tools) and HTTP/SSE (Plug-based, no Phoenix)
• ToolProvider -- auto-derive MCP tools from widget trees (15 widgets)
• FocusLens -- attention-aware tool filtering (focused/all/hover modes)
• ResourceProvider -- expose TEA model state as MCP resources
• Test Harness -- pipe-friendly API (click, type_into, assert_widget), functor law property tests
• Circuit Breaker -- 3-state ETS machine for flaky tool callbacks

Quick Start

# Register a tool
Raxol.MCP.Registry.register_tool(%{
  name: "my_tool",
  description: "Does a thing",
  input_schema: %{type: "object", properties: %{}}
})

# Start MCP server on stdio
mix mcp.server

Architecture

• Raxol.MCP.Server -- GenServer handling JSON-RPC dispatch
• Raxol.MCP.Registry -- ETS-backed registration (tools, resources, prompts)
• Raxol.MCP.Protocol -- JSON-RPC 2.0 encode/decode
• Raxol.MCP.Transport.Stdio -- stdio transport for CLI
• Raxol.MCP.Transport.SSE -- HTTP/SSE transport (Plug)
• Raxol.MCP.Client -- consume external MCP servers
• Raxol.MCP.ToolProvider -- widget-to-tool derivation behaviour
• Raxol.MCP.Test -- test harness with assertions

See main docs for full examples.