Transport: a stdio MCP server built on the official mcp Ruby SDK.
Your agent client starts it and talks JSON-RPC over stdin and stdout. Nothing listens on a network port.
Schema: read from db/schema.rb with a static parser. It never loads your app or connects to a
database, so it’s fast and safe on any checkout. Apps that use db/structure.sql get a best-effort SQL parse.
Routes: generated by your app itself (bin/rails routes --expanded), so engines and route concerns
resolve exactly as Rails sees them. It runs with Bundler’s environment cleared, so the app uses its own
Gemfile. A saved dump or a custom command covers apps that can’t boot locally.
Read-only: both tools are annotated read-only and idempotent, and neither writes files or touches the
database. install-skills is the only command that writes, and only into .cursor/skills/ or
.claude/skills/.
Skill: a Markdown Agent Skill copied into your app. It tells the agent to call these tools before it
writes model attributes, queries, URL helpers or migrations.