Cursor Rules live in project or user rules and show up in almost every chat: language, forbidden directories, style. Keep them short so the agent does not drift.
A skill is a SKILL.md: when to fire, what to read first, a checklist, and bans. The agent follows it when the task matches — deploy, open a PR, review.
Do not stuff a long workflow into Rules, and do not keep “never commit secrets” only inside one skill. Stable constraints go in Rules; reusable steps go in skills.
Write three short rules, then install one development skill from this directory. If the agent ignores it, read the SKILL.md and Cursor skill guides on this site.