OCaml MCP

Supercharge OCaml development with AI coding agents. This MCP server gives AI assistants deep integration with your OCaml projects through Dune, Merlin, and other OCaml Platform tools.

What is MCP?

MCP is an open protocol that enables AI models to securely access local services and tools. This project provides both the core protocol implementation for OCaml and a ready-to-use development server.

Project Overview

This repository contains:

• Protocol Libraries - Build your own MCP servers and clients in OCaml

  • 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 Development Server

  • ocaml-mcp-server - Ready-to-use MCP server with OCaml development tools

Installation

opam install ocaml-mcp-server

Usage

# Using stdio
ocaml-mcp-server

# As an HTTP server
ocaml-mcp-server --socket 8080

Features

The ocaml-mcp-server provides comprehensive OCaml development tools:

Dune Build System Integration

• dune/build-status - Real-time build status with error reporting
• dune/build-target - Build specific targets with streaming output
• dune/run-tests - Execute tests with detailed results (🚧 WIP - no tests)

OCaml Code Analysis

• ocaml/module-signature - Get module signatures from compiled artifacts
• ocaml/find-definition - Jump to symbol definitions (🚧 WIP - no tests)
• ocaml/find-references - Find all usages of a symbol (🚧 WIP - no tests)
• ocaml/type-at-pos - Get type information at cursor position (🚧 WIP - no tests)
• ocaml/project-structure - Analyze project layout and dependencies
• ocaml/eval - Evaluate OCaml expressions in project context

File System Tools (with OCaml superpowers)

• fs/read - Read files with automatic Merlin diagnostics for OCaml code
• fs/write - Write files with automatic OCaml formatting
• fs/edit - Edit files while preserving OCaml syntax validity

The server integrates with Merlin, Dune RPC, ocamlformat, and other OCaml Platform tools.

MCP Protocol 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)

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

License

ocaml-mcp is available under the ISC License.