The body is lean—only one brief intro sentence—defers detail to references, and assumes Claude's competence without explaining what landmarks are, matching the lean-and-efficient anchor.

Quick Reference and Fix give concrete, specific guidance naming exact elements and attributes (e.g., "Replace generic <div> containers with semantic landmark elements like <header>, <nav>, <main>, and <footer>" and "aria-label"), which is actionable for an instruction-only skill without penalizing the deferred code.

The Check/Fix/Explain/Code Review structure lays out an unambiguous single-purpose review workflow; per the simple-skills note, a clear single-action workflow can score 3, and no destructive/batch operation requires validation checkpoints.

The under-50-line body is well-organized into clear sections and points to a real one-level-deep reference ("see references/rule.md", verified present), satisfying the clear-overview-with-well-signaled-references anchor.

The description lists multiple concrete actions—"Check native semantics first, then inspect keyboard behavior, focus flow, accessible names, and screen-reader output"—matching the anchor for several specific concrete actions rather than vague domain-only phrasing.

It answers both what ("Check native semantics first, then inspect keyboard behavior, focus flow, accessible names, and screen-reader output") and when via an explicit "Use when reviewing rendered HTML..." trigger clause, satisfying the both-what-and-when anchor.

It includes relevant terms like "rendered HTML, interactive components, or design-system patterns," but these lean generic and the embedded literal title phrase "Use landmark regions correctly" is awkward rather than natural, leaving common variations uncovered.

The narrow landmark focus gives it a niche, but the broad review scope ("rendered HTML, interactive components, or design-system patterns") overlaps with other accessibility skills, fitting the somewhat-specific-but-overlapping anchor.