This is meta tooling for Codex itself. It lets you browse and install skills from the curated openai/skills repository or pull them from any other GitHub repo, including private ones. The main workflow is straightforward: list what's available, pick what you want, and it handles the download into your skills directory. It's smart enough to try direct downloads first and fall back to git sparse checkout if authentication is needed. The curated list lives at github.com/openai/skills in the .curated folder, and system skills come preinstalled. You'll need to restart Codex after installing anything new. Honestly, if you're extending Codex regularly, you'll use this constantly.
npx skills add https://github.com/aiskillstore/marketplace --skill skill-installer