"Well-organized markdown docs" are exactly what skills are.

More specifically, they are well-organized markdown docs that explain how to do some particular thing.

They're presented as a list of titles and descriptions to the LLM and it can pick which ones seem relevant and load them.

Markdown docs the LLM needs to make a tool call to read the files and potentially multiple tool calls to discover data if there's a hierarchy. Additionally, it now has to decide if it should read the entire file or cherry pick parts of it.

Skills organize that in an atomic and composable way.

I think ChatGPT and Claude skills will also package arbitrary artifacts like scripts as well. Not sure if that's standard or not

After that, I think "skill" is just a good name. It sounds more "AI" than a "spell" or "incantation", which would sound magical and esoteric.