The key here is “on demand”. Not every agent or convention needs to know kung fu. But when they do, a skill is waiting to be consumed. This basic idea is “progressive disclosure” and it composes nicely to keep context windows focused. Eg i have a metabase skill to query analytics. Within that I conditionally refer to how to generate authentication if they arent authenticated. If they are authenticated, that information need not be consumed.

Some practical “skills”: writing tests, fetching sentry info, using playwright (a lot of local mcps are just flat out replaced by skills), submitting a PR according to team conventions (eg run lint, review code for X, title matches format, etc)