rigortype/rigor/rigor-mcp-setup

Rigor MCP Setup

rigor mcp is the Model Context Protocol server bundled with the rigortype gem. It exposes Rigor's analysis as JSON-RPC tool calls over stdio, so an AI coding agent can call Rigor directly during a session — check types before a refactor, look up the type at a cursor, or triage a project's diagnostics as review context. All tools are read-only (write-side commands like rigor init / sig-gen --write are deliberately excluded — modifying files stays the developer's call).

The authoritative, per-client configuration lives in the manual. With Rigor installed, read it offline with no network round-trip:

rigor docs mcp-server

(Web fallback, only before Rigor is installed: [Rigor MCP Server — AI Agent Integration](https://github.com/rigortype/rigor/blob/master/docs/manual/10-mcp-server.md).) This skill is the workflow around it (identify the client → apply the manual's snippet → verify the handshake), so it does not duplicate (and cannot stale-out) the config details.

First: load the version-current copy

The config details already come live from rigor docs; this keeps the workflow itself current too. Prefer the copy of this skill that ships with the installed Rigor over any vendored or frozen copy of this file:

rigor skill --full rigor-mcp-setup

If you already loaded this skill via rigor skill you have the current copy — just proceed. If rigor is not on PATH, this task needs it: run `rigor-next-steps` to install Rigor first, then come back.

When to use

• A developer wants their AI agent to call Rigor's tools mid-session.
• A project commits a shared MCP config (.mcp.json, .cursor/mcp.json)

and you want to add Rigor to it for the whole team.

When NOT to use

• Editor (human) integration — that is rigor-editor-setup (rigor lsp).
• The project has no Rigor config yet — run rigor-project-init first

(the MCP tools use the same .rigor.yml discovery as rigor check).

The tools you are wiring in

rigor_check, rigor_type_of, rigor_triage, rigor_annotate, rigor_sig_gen, rigor_explain, rigor_coverage — each the JSON form of the matching rigor CLI command. See the manual's Tool reference for inputs and outputs.

The one stable fact

Every client config simply launches `rigor mcp` (stdio) and needs `rigor` on the agent's `PATH` — the same executable rigor check uses. For agents that do not inherit your shell, the mise shim path is the most reliable channel (see rigor docs install, or Installing Rigor on the web). Do not add rigortype to the project's Gemfile — it is a tool, not a library.

Procedure

Phase 1 — confirm the analyzer works from the CLI first

rigor check <a-file-or-dir>

The MCP tools share rigor check's config discovery. If check works from the project root, the tools will too.

Phase 2 — identify the client and apply the config

Ask the developer which agent they use, or detect a committed config (.mcp.json, .cursor/mcp.json, .claude/settings.json). Apply the matching snippet from the manual's Client wiring section verbatim — it covers Claude Desktop, Claude Code CLI, Cursor, Cline, and a generic stdio client:

rigor docs mcp-server

(or, pre-install, the web copy: <https://github.com/rigortype/rigor/blob/master/docs/manual/10-mcp-server.md>)

Each snippet is the same shape — {"command": "rigor", "args": ["mcp"]}. If the project commits a shared MCP config, add the Rigor entry there and commit it so every contributor gets it.

Working-directory gotcha (from the manual's Troubleshooting): the server discovers config from the directory it is launched in. If the client starts rigor mcp from $HOME or a temp dir, no .rigor.yml is found and tools return an empty set. Pin it with "args": ["mcp", "--config=/abs/path/.rigor.yml"], or pass absolute paths in the tool call.

Phase 3 — verify the handshake

Confirm rigor mcp answers the MCP initialize request:

echo '{"jsonrpc":"2.0","id":0,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"0"}}}' | rigor mcp

A JSON result with serverInfo.name: "rigor" means it works; nothing or a shell error means rigor is not on the PATH the client uses. Then restart the client and confirm the rigor_* tools appear in its tool palette.

Next step

Re-run rigor skill describe for the next move — with the agent able to call Rigor's tools, raising protection (rigor-protection-uplift) or reducing a baseline (rigor-baseline-reduce) is a tighter loop.