Raxol MCP

MCP (Model Context Protocol) server and client for Elixir. JSON-RPC 2.0 protocol, tool/resource registry, stdio and SSE transports. Auto-derives agent tools from your widget tree.

Install

{:raxol_mcp, "~> 2.8"}

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 (16 Component modules implement it)
• 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_component), functor law property tests
• Circuit Breaker: 3-state ETS machine for flaky tool callbacks

Quick start

# Register a tool with the default registry
Raxol.MCP.Registry.register_tools([
  %{
    name: "my_tool",
    description: "Does a thing",
    inputSchema: %{type: "object", properties: %{}},
    callback: fn _args -> {:ok, [%{type: "text", text: "done"}]} end
  }
])

# 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.