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require-skill-frontmatter

Require valid YAML frontmatter with non-empty name and description fields in Codex skills.

Rule catalog ID: R019

Targeted pattern scope​

  • **/.agents/skills/**/*.md
  • Codex plugin skill directories

What this rule reports​

  • Skill frontmatter is not valid YAML: {{error}}
  • Skill frontmatter must declare a non-empty string description that explains what the skill does and when to use it.
  • SKILL.md must start with YAML frontmatter declaring name and description.
  • Skill frontmatter must declare a non-empty string name.

Why this rule exists​

Require valid YAML frontmatter with non-empty name and description fields in Codex skills.

❌ Incorrect​

A file in the targeted scope that produces any diagnostic listed above is incorrect for this rule.

✅ Correct​

A file is correct when it uses the documented Codex structure and produces no diagnostic from this rule.

Behavior and migration notes​

Included in:

  • codex.configs.minimal
  • codex.configs.recommended
  • codex.configs.strict
  • codex.configs.all

ESLint flat config example​

The preset layers supply the correct Markdown, TOML, or JSON language configuration. Override the rule only in a later matching flat-config entry:

import codex from "@typpi/eslint-plugin-codex";

export default [
 ...codex.configs.recommended,
 {
  rules: { "codex/require-skill-frontmatter": "error" },
 },
];

Further reading​