Conciseness

The body glosses concepts Claude already knows — e.g., "POUR 原則: WCAG の基盤（知覚可能・操作可能・理解可能・堅牢）", "アクセシビリティツリー: 支援技術が実際に「読み取る」UI の表現", and the alt-text rationale "スクリーンリーダーはすでに「画像」というロールをアナウンスする" — making it 'mostly efficient but with some unnecessary explanation' (anchor 3). It is above anchor 2 because the bulk is dense, skill-specific guidance (SC numbers, ratios, pixel sizes) rather than padding, but the Core Concepts glossary and anti-pattern rationale are more than the 'minor instances' required for anchor 4.

Actionability

Concrete, executable guidance dominates: three copy-paste-ready examples (HTML search form, SwiftUI button, Kotlin Switch), a cross-platform mapping table with exact API calls, and specific values ("4.5:1", "24x24 CSS ピクセル", SC 2.5.8/2.4.11/3.3.7). This fits anchor 4 ('mostly executable, minor gaps') rather than 5 because checklist items like focus trapping, focus restoration, and error suggestions have no accompanying code or commands.

Workflow Clarity

The 仕組み section gives a clear five-step sequence (role identification → perceivable → operable → understandable → robust) and the closing checklist acts as an explicit verification checkpoint. It matches anchor 4 ('clear sequence, most checkpoints present, minor validation gaps') — the checklist is end-of-process rather than per-step, and no audit/testing method for verifying compliance is given — but the sequence is more complete and better defined than anchor 3.

Progressive Disclosure

The skill has no bundle files (references/, scripts/, assets/ are absent), so everything lives in a single ~140-line SKILL.md with well-organized sections and a clearly labeled external-links section. Structure and placement are good (anchor 4); it cannot reach anchor 5 because there are no one-level-deep reference files and the under-50-line simple-skill exception does not apply, though nothing here clearly demands splitting into separate files.

Specificity

The description lists several concrete actions — "設計・実装・監査します" (designs, implements, audits) and generating "セマンティック ARIA" and "アクセシビリティトレイト" — anchored to a named standard ("WCAG 2.2 レベル AA"). This matches anchor 4 (several specific actions, minor gaps) rather than 5, since coverage is not fully comprehensive (e.g., no mention of audit reports, contrast checking, or remediation guidance).

Completeness

Both 'what' ("設計・実装・監査します...ARIA...トレイトを生成") and 'when' ("生成するために使用します") are explicitly present, satisfying anchor 4. It falls short of anchor 5 because the 'when' clause covers only generating ARIA/traits and omits trigger guidance for auditing or compliance-gap work, which the 'what' half advertises.

Trigger Term Quality

Natural keywords include "WCAG 2.2", "アクセシビリティ", "ARIA", and "iOS/Android", which users would plausibly say when needing this skill. A few common variations are missing (e.g., "a11y", "スクリーンリーダー", "コンプライアンス", "Section 508"), placing it at anchor 4 rather than 5.

Distinctiveness Conflict Risk

The description occupies a clear niche (WCAG 2.2 AA compliance, ARIA, iOS/Android accessibility traits) with distinct triggers that would not naturally fire for sibling skills like `frontend-patterns` or `design-system`. Anti-drift check against anchor 4 confirms minimal, not merely minor, overlap risk.