Codex CLI 0.166.0 was released on 29 October 2026. If you are checking local skills while reviewing that release, validate the file header before rewriting the workflow. The metadata rules below come from the current Agent Skills specification; the CLI release is not claimed to have changed them.
A folder with instructions is not automatically a valid agent skill. The open Agent Skills specification requires a SKILL.md file with YAML frontmatter followed by Markdown. A formatting problem can prevent the host from recognizing what you intended.
Validate the small header first
For a folder named weekly-brief, a minimal header includes name: weekly-brief and a nonempty description explaining the job and when to use it. The name must match the parent directory and follow the specification’s naming rules. Keep the opening and closing frontmatter separators on their own lines.
Ask the assistant to inspect the file as text before altering its procedure. Check missing fields, accidental indentation and a name copied from another example. Use the host’s documented validator or refresh process; merely finding the file on disk is not a successful discovery check.
Confirm discovery without a real task
Refresh the skill list and inspect the displayed description and path. If it still fails, preserve the validation message and change only the identified cause. Do not run the skill on private documents just to see whether installation worked. Metadata validation and the later quality check of its actual output are separate steps.
These checks concern local skill authoring in Codex CLI and other hosts that implement the standard. Plugin distribution and account access are separate. Codex detects skill changes automatically; if a change does not appear, the current guide recommends restarting Codex. Do not change permissions to repair a YAML error.