Their non-skill based "compressed index" is just similarly "Each line maps a directory path to the doc files it contains" but without "skillification." They didn't load all those things into context directly, just pointers.

They also didn't bother with any more "explanation" beyond "here are paths for docs."

But this straightforward "here are paths for docs" produced better results, and IMO it makes sense since the more extra abstractions you add, the more chance of a given prompt + situational context not connecting with your desired skill.

You could put the name and explanation in CLAUDE.md/AGENTS.md, plus the path to the rest of the skill that Claude can read if needed.

That seems roughly equivalent to my unenlightened mind!

I like to think about it this way, you want to put some high level, table of contents, sparknotes like stuff in the system prompt. This helps warm up the right pathways. In this, you also need to inform that there are more things it may need, depending on "context", through filesystem traversal or search tools, the difference is unimportant, other than most things outside of coding typically don't do filesystem things the same way