The body is lean: terse Quick Reference bullets and one-line Check/Fix/Explain/Code Review directives, with no explanation of concepts Claude already knows. The brief opening justification ('improving LCP by 100-300ms on average') is light and every token roughly earns its place, matching 'Lean and efficient; assumes Claude's competence.' Not level 2 because there is no unnecessary explanation or padding; clearly not level 1.

The body names specific hint types and use cases ('Use preload for critical above-the-fold resources (fonts, hero images)', 'Add appropriate resource hints (preload, prefetch, preconnect)'), but the executable code and concrete commands are deferred to references/rule.md rather than present in the body. Matches 'Some concrete guidance but incomplete; missing key details.' Not level 3 because there is no copy-paste-ready code in the body; not level 1 because the guidance is concrete and specific rather than abstract.

The Check/Fix/Explain/Code Review sections imply an audit-then-fix-then-review ordering, and Code Review mentions 'the measurement method used to confirm the issue', but there is no explicit sequenced workflow with validation checkpoints or a fix-and-revalidate feedback loop in the body. Matches 'Steps listed but validation gaps; checkpoints missing or implicit.' Not level 3 because validation is implicit rather than an explicit checkpoint sequence; not level 1 because an ordering and a measurement notion are present.

The body is a concise overview that points to a single real, well-signaled reference ('see references/rule.md'), which exists and is well-organized one level deep. Matches 'Clear overview with well-signaled one-level-deep references; content appropriately split; easy navigation.' Not level 2 because the reference is clearly signaled and the split is appropriate; not level 1 because there is no monolithic wall of text or nested references.

Names a concrete domain ('auditing slow page loads, heavy assets, or rendering delays') and tools ('DevTools, Lighthouse, or field data'), but it describes triggering conditions rather than a comprehensive list of specific skill actions, matching 'Names domain and some actions, but not comprehensive.' It is not level 3 because there is no enumeration of multiple concrete capabilities the skill performs, and not level 1 because the language is concrete rather than vague.

It answers both 'what' ('Verify the actual bottleneck... before recommending changes') and 'when' with an explicit 'Use when...' trigger clause ('Use when auditing slow page loads, heavy assets, or rendering delays'), matching the anchor for clearly answering both with explicit triggers. Not level 2 because the 'when' is explicit rather than implied; not below 3 because the 'Use when' clause is present.

It includes reasonably natural terms a user would say ('slow page loads', 'heavy assets', 'rendering delays', 'DevTools', 'Lighthouse'), but common variations like 'performance', 'load time', 'slow site', or 'Core Web Vitals' are missing, so coverage is incomplete rather than strong. Not level 3 because the natural-term coverage is partial; not level 1 because the terms present are genuinely user-facing rather than technical jargon.

The resource-hints framing ('resource hints for faster loading') and measurement tooling give it a recognizable niche, but the triggers ('slow page loads', 'heavy assets', 'rendering delays') could overlap with general performance-auditing skills. Matches 'Somewhat specific but could still overlap with similar skills.' Not level 3 because the triggers are not uniquely distinctive; not level 1 because the niche is identifiable and not broadly generic.