This lets Claude delegate tasks to codex, an AI coding agent that can execute commands in a sandboxed environment. It checks if codex is installed, then sends your task description for execution using the danger-full-access sandbox mode. The obvious use case is when you need actual code execution or filesystem operations that Claude can't handle directly. Fair warning though, the source is pretty bare bones. It's essentially a wrapper that shells out to codex with whatever task description you provide, and it notes the operation might take a while. If you're already using codex in your workflow and want Claude to be able to call it, this does exactly that. Just be aware you're giving it full access permissions.
npx skills add https://github.com/dotneet/claude-code-marketplace --skill call-codex