xAI's docs say a useful skill states six things: when to use it, the inputs and access it needs, the order of work, how to check the result, what to return, and what needs approval (source). Private skills form one library shared by all your Bots. Type / in the desktop composer to use one.
Skill template
Skill: [name] When to use: [trigger or request] Inputs and access: [files, connectors, logins the Bot needs] Steps: 1. [step] 2. [step] Validate: [checks that prove the result is right] Return: [exact output format and where to post it] Needs approval: sending, publishing, purchasing, deleting, or changing live systems If data is missing or stale: stop and report. Do not guess.
Every recipe on this site follows this structure. The Business Skills Pack includes all of them as ready-made skill files.