Skills can be about as deterministic. Consider GitHub MCP vs skill for GH CLI.

It might use the view_pr tool, or `gh pr view`, but in the end it's still performing a deterministic action.

The benefit might be that the GH skill can contain more domain specific information about GitHub, and you only pay the context cost when the skill is read.

Personally I generally avoid MCP and have skills for CLIs -- if one doesn't exist, then I author one. For example I have a CLI for Grafana, Discord, Sentry, etc.

https://github.com/shepherdjerred/monorepo/tree/main/package...