If you're building anything on Medusa's backend, load this before you start writing code. It enforces the critical architecture pattern (modules feed workflows, workflows feed routes, never skip layers) and catches the mistakes that break Medusa apps: using PUT/PATCH instead of POST/DELETE, calling module services directly from routes, forgetting that workflows can't use async/await or conditionals in their composition functions, and filtering linked module data with query.graph() instead of query.index(). The real value is in the reference files it points you to, each one specific to what you're implementing. Also worth noting: prices in Medusa are stored as-is, not in cents, which trips up everyone at least once.
npx skills add https://github.com/medusajs/medusa-claude-plugins --skill building-with-medusa