Just ask it to.

/init in Claude Code already automatically extracts a bunch, but for something more comprehensive, just tell it which additional types of things you want it to look for and document.

> Did you have to develop these skills yourself? How much work was that? Do you have public examples somewhere?

I don't know about the person above, but I tell Claude to write all my skills and agents for me. With some caveats, you can do this iteratively in a single session ("update the X agent, then re-run it. Repeat until it reliably does Y")