OCaml MCP

OCaml implementation of the Model Context Protocol (MCP), enabling integration between AI assistants and development tools.

Quick Start

# Install
opam install  ocaml-mcp-server

# Terminal 1 - Start server
ocaml-mcp-server --socket 8080

# Terminal 2 - Use client
mcp call "dune/build-status" --socket 8080
mcp call "ocaml/module-signature" --socket 8080 \
  -a '{"module_path": ["List"]}'

Libraries

• mcp - Core protocol implementation (types, client, server)
• mcp-eio - Transport layer (stdio, socket, memory, HTTP)
• mcp-sdk - High-level SDK for building MCP servers and clients
• ocaml-mcp-server - OCaml development tools server

Implementation Status

✅ Implemented

• Core protocol types and JSON-RPC messaging
• Client/server request-response patterns
• Notification handling
• Transport layer (stdio, socket, memory, HTTP)
• Server-to-client request handling (sampling, elicitation, roots)
• High-level SDK with type-safe tool/resource/prompt registration
• Dynamic JSON schema generation from OCaml types
• OCaml development tools (Dune build status, module signatures from build artifacts)
• Full compliance with MCP 2025-06-18 specification

🚧 In Progress / Missing

High Priority:

• OAuth 2.1 authentication - Security for production use

Feature Parity:

• Request lifecycle:
  • Timeouts
  • Cancellation - Currently not supported. The protocol defines $/cancel notifications, but implementing proper cancellation requires thread-safe cancellation tokens and checking cancellation status during long operations
  • Progress tracking (basic support implemented)
• Argument completion support
• WebSocket and SSE transports
• Some client helper functions (resources/subscribe, completion/complete, logging/setLevel, ping)

Examples

See the examples/ directory for complete working examples:

• weather-server - A minimal MCP server that provides weather information

License

ocaml-mcp is available under the ISC License.