Conciseness

The body is lean and terse (Check/Fix/Explain/Code Review are each 1-2 sentences), but the intro sentence "Image CDNs automatically optimize, resize, and convert images on-the-fly..." explains a concept Claude already knows and partially duplicates the Quick Reference bullets. Minor over-explanation to trim keeps this at 4 rather than 5.

Actionability

The body gives direction with some concrete anchors ("Configure an image CDN like Cloudinary, Imgix, or Cloudflare Images", "Flag exact files or components where format choice, sizing, or loading behavior violates the rule") but contains no code, commands, or concrete verification steps itself — the executable material is one reference hop away in references/rule.md. Some concrete guidance but missing key details matches anchor 3; it is not 2 because specific providers and review targets are named.

Workflow Clarity

This is a simple, single-purpose review skill with an unambiguous action, and the Check -> Fix -> Explain -> Code Review sections present a clear sequence. It is not 5 because the verification checkpoints are implicit in the body (the actual 5-step verification checklist lives in references/rule.md and is not surfaced or linked from the Check section); it is above 3 because the sequence and deliverable are clear and the operation is non-destructive.

Progressive Disclosure

A short, well-organized overview body with a single clearly signaled, one-level-deep reference: "For full implementation details, code examples, and framework-specific guidance, see references/rule.md" — and that file exists, contains the implementation details (provider URL examples, Next.js config, responsive patterns, verification steps), and does not nest further references. Content is appropriately split and navigation is easy, matching anchor 5.

Specificity

"Check encoded size, rendered size, loading strategy, and above-the-fold impact together" and "reviewing image assets, markup, and CDN or build transforms" list several concrete actions with concrete nouns. It falls short of 5 because coverage is not comprehensive (e.g., the fix/explain capabilities present in the body are absent), but exceeds 3 because more than 1-2 specific actions are named.

Completeness

Both parts are explicit: "Use when reviewing image assets, markup, and CDN or build transforms related to Serve images from a CDN" answers when with concrete trigger phrases, and "Check encoded size, rendered size, loading strategy, and above-the-fold impact together" answers what. The 'when' clause is more explicit and specific than the anchor-4 example, matching anchor 5's clearly-explicit both-what-and-when pattern.

Trigger Term Quality

Natural terms users would say are present: "image assets", "markup", "CDN", "build transforms", "loading strategy", "above-the-fold". It is not 5 because common synonyms and variations are missing ("image optimization", "responsive images", "lazy loading", "WebP", "AVIF"), but it is well beyond the sparse keyword coverage of anchor 3.

Distinctiveness Conflict Risk

"Serve images from a CDN" carves a clear niche distinct from most skills, but the shared check list (encoded size, rendered size, loading strategy) overlaps with closely related image rules (modern formats, lazy loading, responsive images). Mostly distinct with minor overlap risk, so 4 rather than 5.