The ocaml.org MCP Server: OCaml Package Data for AI Assistants

ocaml.org hosts a public Model Context Protocol (MCP) server that lets AI assistants — such as Claude, ChatGPT and Gemini, in both their web apps and local clients — query OCaml package data directly. The server is reached over public HTTPS from the assistant's side, so wiring it in takes only a URL: there is no local install and no OCaml environment required.

The endpoint is:

https://ocaml.org/mcp

It speaks Streamable HTTP (JSON-RPC 2.0 over an HTTP POST, with a companion GET for the server-to-client stream), which is the transport remote MCP clients use. The server is public, read-only and stateless: it exposes data ocaml.org already computes and holds no per-session state.

Available tools

The first capability shipped is package dependency information, which ocaml.org can answer authoritatively because it already computes it in memory for every package in the opam repository.

• ocaml_package_dependencies — the direct dependencies (with their version constraints), optional dependencies and conflicts of a package. Takes a package name and an optional version (defaulting to the latest release).
• ocaml_package_reverse_dependencies — the packages that depend on a given package ("used by"), each with its version constraint and latest release, plus a total count. Takes the same arguments.

Each tool returns a JSON document. For example, asking ocaml_package_dependencies about dream returns that package's resolved version alongside its dependencies, optional and conflicts lists.

More tools — API and module documentation, and documentation search — are planned; see the tracking issue for the roadmap.

Connecting your assistant

Whether you can add a remote MCP server, and where, depends on your assistant and plan. The steps below cover the three most common clients.

Claude

Remote MCP connectors are available to Claude users on all plans, in both Claude.ai and Claude Code. In the web or desktop app, open Settings → Connectors → Add custom connector, give it a name (for example "ocaml.org") and paste the URL https://ocaml.org/mcp. In Claude Code, run:

claude mcp add --transport http ocaml-org https://ocaml.org/mcp

ChatGPT

ChatGPT reaches custom MCP servers through Developer Mode. Enable it under Settings → Connectors → Advanced → Developer mode, then add a new connector pointing at https://ocaml.org/mcp. Custom connector availability depends on your ChatGPT plan.

Gemini

Gemini's support for custom MCP servers is oriented towards its enterprise and developer tooling (for example the Gemini CLI and Vertex AI Agent Engine) rather than the consumer app. Point your MCP-capable Gemini client at https://ocaml.org/mcp following its connector configuration.

Notes

The endpoint is public and rate-limited per client. It only ever reads from ocaml.org's own package data, so it cannot be used to fetch arbitrary URLs. Because the assistant connects from its vendor's cloud, the server cannot see your local machine: it is not a substitute for local tooling that inspects your current opam switch, pins or installed packages.