You add a new SKILL.md under .cursor/skills/ while Cursor is running, then type / in chat and find the skill missing from the list. Rewriting the file twice changes nothing. What explains it?

The principle — Skill discovery is a startup activity. When Cursor starts, it automatically discovers skills from skill directories and makes them available to Agent, so a folder created after launch can be perfectly valid and still be invisible.

Why the key is correct — Restarting is the cheap first check and it matches the symptom exactly: nothing about the file's contents can make an undiscovered skill appear, which is why two rewrites achieved nothing. Once discovery has run, the skill shows up when you type a slash in chat, and the Agent can also select it on relevance, judged from the description in the frontmatter.

Why the others are wrong — There is no manifest to register a skill in; the folder holding SKILL.md is the registration. There is no enabled-skills setting that new folders start outside either, since Customize reports what discovery found rather than gating it. And skills do not load through rules, so reading rule files looking for an import will find nothing to fix.

Remember this — When a new skill is missing, restart first. Then confirm SKILL.md sits directly inside its own folder and that the folder name matches the name in the frontmatter.

Sources — Cursor's Agent Skills documentation.