The ~33-line body is lean and sectioned (Quick Reference, Check, Fix, Explain, Code Review) without explaining concepts Claude already knows (e.g., what CSS is); every section earns its place.

As an instruction-only skill it gives concrete, specific guidance — "Use semantic HTML", "Keep DOM order aligned with reading order", "Do not put essential labels... in CSS generated content", "Test key journeys with author styles disabled" — which is actionable per the instruction-skill carve-out despite the absence of code.

The simple single-purpose review task follows a clear Check → Fix → Explain → Code Review sequence with a verification checkpoint ("note how to verify the fix with styles disabled"), satisfying the simple-skill allowance without needing batch/destructive feedback loops.

The SKILL.md is a concise overview that clearly signals a one-level-deep reference ("see `references/rule.md`"), and that referenced file exists, giving clean navigation without nested references.

The description lists multiple concrete actions — "Check the DOM order, semantic structure, form relationships, and whether CSS generated content carries essential information" — matching the anchor for listing several specific concrete actions rather than a single vague action.

It answers both what ("Check the DOM order, semantic structure, form relationships...") and when via an explicit "Use when reviewing rendered HTML, layout components, or design-system patterns..." trigger clause, satisfying the requirement for explicit triggers.

It surfaces natural terms a frontend/accessibility reviewer would say — "rendered HTML", "layout components", "design-system patterns", "DOM order", "semantic structure", "CSS generated content" — giving good coverage rather than only generic or jargon-only phrasing.

The CSS-independent-content / accessibility niche is narrow with distinct triggers (presentation-for-meaning checks), making it unlikely to fire for unrelated skills.