Not quite the same thing. Implementing skills specifically means that you have code which, on session start, scans the skills/*/skill.md files and reads in their description: metadata and loads that into the system prompt, along with an instruction that says "if the user asks about any of these particular things go and read the skills.md file for further instructions".

Here's the prompt within Codex CLI that does that: https://github.com/openai/codex/blob/ad7b9d63c326d5c92049abd...

I extracted that into a Gist to make it easier to read: https://gist.github.com/simonw/25f2c3a9e350274bc2b76a79bc8ae...