How to write good skills

I've been writing AI tooling skills for a while now, and a few things keep coming up as the difference between a skill that gets reused and one that gets ignored.

Be specific about the trigger

A skill should make it obvious when it applies. Vague triggers lead to the agent either never using the skill, or using it when it shouldn't.

Keep the instructions actionable

Write the skill like you're handing instructions to a competent engineer who has zero context on your codebase. Concrete steps beat abstract principles.

Iterate based on real usage

The best skills are the ones that evolve after you watch them fail in practice.