skill-creator: Invalid YAML in frontmatter

What version of Codex is running?

codex-cli 0.77.0

What subscription do you have?

Pro

Which model were you using?

gpt-5.2-codex

What platform is your computer?

Linux 6.17.9-arch1-1 x86_64 unknown

What issue are you seeing?

Skill skill-creator produced a SKILL.md with a collon followed by a space within the description itself, which caused it to be parsed as invalid YAML. Codex then skips loading the skill with an "invalid YAML" error.

What steps can reproduce the bug?

1. Do not have PyYAML installed.
2. Use skill-creator to create a new skill.
3. Get unlucky that the AI model writes a description that includes YAML syntax, or perhaps explicitly tell it to use a description such as "something: something else", and get unlucky that the AI model doesn't realize it needs to quote the description.
4. Restart Codex, and observe the skill loading error.

What is the expected behavior?

The skill-creator SKILL.md should try preventing invalid YAML frontmatter.

Additional information

At the time, I didn't have PyYAML installed. I see quick_validate.py would have said this was invalid, and perhaps that would have made Codex fix the error. Even so, some users won't have PyYAML installed and additional instruction could prevent this issue. Additionally, saving a validation failure on a system with PyYAML and generating it correct the first time is preferable.