Expert habits, written down.
Each skill is one Markdown file your assistant loads when it's relevant. It says what to ask you, how to do the work, the format to use, and the mistakes that make that kind of note fail.
You never have to call one by name. Ask for "something I can study from" and your assistant notices it has a skill for that. And none of them invents a fact: anything missing is marked, so you can fill it in.