Conciseness

The body is lean and focused on tool-specific knowledge Claude would not already know (pageId requirement, the .md.txt URL trick, report-parsing via a node one-liner, the headless contrast caveat). Not anchor 5 only because of a few trimmable phrases such as "This is much easier to read!" and "This efficiently extracts the selector and snippet..." which restate the adjacent instruction; it is well above anchor 3 since virtually no general-concept padding exists.

Actionability

Guidance is fully executable: exact tool names with exact parameters ("types: [\"issue\"]", "includePreservedMessages: true", press_key with "Tab"/"Shift+Tab"), a copy-paste-ready node one-liner for filtering the Lighthouse report (with the path placeholder explicitly flagged), and named, verified snippets in references/a11y-snippets.md for orphaned inputs, tap-target sizing, contrast, and global checks. Common cases are covered concretely, matching anchor 5.

Workflow Clarity

The eight numbered workflow patterns are clearly sequenced, starting from an explicit baseline ("Start by running a Lighthouse accessibility audit"), with explicit validation checkpoints in each ("A score < 1 indicates violations", "Ensure heading levels... do not skip levels", "Locate the element marked as focused... to verify focus moved"), a fallback feedback loop in the contrast pattern ("If native audits do not report issues... use evaluate_script"), and a Troubleshooting section for error recovery — matching anchor 5's sequence + validation + feedback-loop criteria.

Progressive Disclosure

SKILL.md serves as a clear overview and appropriately pushes the bulk executable code (four snippet implementations) into references/a11y-snippets.md, which exists, is one level deep, and its snippet titles match the names cited in the body. References are well signaled via bold snippet names plus markdown links, and sections (Core Concepts, Workflow Patterns, Troubleshooting) are easy to navigate, matching anchor 5.

Specificity

The description names the domain and tool ("Uses Chrome DevTools MCP for accessibility (a11y) debugging and auditing based on web.dev guidelines") but the stated actions — "debugging and auditing" — are generic; it never lists concrete operations like running Lighthouse audits, capturing accessibility-tree snapshots, or checking contrast ratios. This matches anchor 3 (domain plus 1-2 generic actions) better than anchor 4, which expects several specific actions listed.

Completeness

Both what and when are explicitly present: what is "Uses Chrome DevTools MCP for accessibility (a11y) debugging and auditing based on web.dev guidelines" and when is "Use when testing semantic HTML, ARIA labels, focus states, keyboard navigation, tap targets, and color contrast" with concrete triggers. Falls just short of anchor 5 because the 'what' side is abstract ("debugging and auditing") rather than enumerating concrete actions as the anchor-5 example does; it is clearly above anchor 4's 'when could be more explicit' weakness since the when-clause is highly specific.

Trigger Term Quality

Strong natural triggers users would actually say: "semantic HTML, ARIA labels, focus states, keyboard navigation, tap targets, and color contrast", plus the "a11y" abbreviation. Not anchor 5 because common natural terms like "screen reader", "WCAG", or "accessibility audit/report" are missing.

Distinctiveness Conflict Risk

The a11y/DevTools-MCP niche and triggers like "ARIA labels", "tap targets", and "color contrast" are mostly distinct with minimal conflict risk. Not anchor 5 because broader terms like "semantic HTML", "focus states", and "keyboard navigation" could also plausibly match general web-testing or frontend-development skills.