Conciseness

The body is ~740 lines, with ~500 of them an inline HTML skeleton library, and key guidance repeated several times: the no-text rule appears in the Overview ("no titles, no subtitles, no body copy"), the 'One Big Rule' section, the step-2 rules ("No text characters at all"), and the visual checklist ("Zero text. No letters."); the 'pick the primary outcome' advice is stated twice nearly verbatim ("pick the one that matches the **primary outcome**" at both the Skeleton Library intro and 'Picking A Skeleton'). Mostly efficient and free of concept-explanation padding, but more than minor trimming is warranted — matching the level-3 anchor rather than level 4's 'minor instances'.

Actionability

Fully executable, copy-paste-ready throughout: the exact scoped sed command for the dark variant, exact node invocations with --input/--output paths, `npm run verify:images`, concrete agent-browser commands (open/eval/screenshot), a complete base HTML template, and six complete skeleton HTML blocks. Not 4: there are no gaps — even the output directory choice and recipes.ts wiring snippets are given verbatim.

Workflow Clarity

A clear 8-step numbered workflow with explicit validation checkpoints and feedback loops: step 4 'Verify The Contract' (`npm run verify:images` must pass), step 6-7 visual verification via agent-browser with a 6-item checklist and 'If any answer is "no", iterate on the HTML and re-render', plus a 'Failure Modes And Fixes' section mapping each failure to its fix. Matches the level-5 anchor exactly.

Progressive Disclosure

No references/, scripts/, or assets/ bundle directories exist — everything lives in a single ~740-line SKILL.md, and the ~500-line skeleton library plus base template is content that clearly belongs in a separate file (e.g. references/skeletons.md), with the body keeping only the picking table. Section structure and navigation are good, which fits the level-3 anchor ('some structure... content that should be separate is inline') better than level 2 (which implies no organization) or level 4 ('most content is appropriately placed').

Specificity

Quotes multiple specific concrete actions with comprehensive coverage: "Generate on-brand 16:9 placeholder preview images for DevHub resources (recipes, cookbooks, examples)", "Produces a light and a dark PNG at 1920x1080 that passes `npm run verify:images`", "wires the images into `src/lib/recipes/recipes.ts`", and "verifies them with agent-browser". Unlike the level-4 anchor, there are no gaps in coverage — generate, verify, wire, and re-verify are all named.

Completeness

Explicitly answers both: what — "Produces a light and a dark PNG at 1920x1080 that passes `npm run verify:images`, wires the images into `src/lib/recipes/recipes.ts`, and verifies them with agent-browser" — and when — "when a real app screenshot is not available. Use when you need to add, regenerate, or improve a resource's previewImageLightUrl / previewImageDarkUrl". Clear what-and-when with concrete trigger phrases, matching the level-5 anchor; level 4 would require the 'when' to be less explicit.

Trigger Term Quality

Good keyword coverage with natural phrases: "placeholder preview images", "recipes, cookbooks, examples", "add, regenerate, or improve", "previewImageLightUrl / previewImageDarkUrl", "real app screenshot". Not 5 because a few natural synonyms users might say are missing (e.g. thumbnail, hero image, card art, fallback art); not 3 because the concrete field names and add/regenerate/improve variations go well beyond 'some relevant keywords'.

Distinctiveness Conflict Risk

Clear niche with distinct triggers: scoped to DevHub resource preview images with repo-specific artifacts (`npm run verify:images`, `src/lib/recipes/recipes.ts`, agent-browser), so minimal conflict risk with other skills. Not 4: no meaningful overlap with closely related skills since the triggers are uniquely tied to this repo's field names and workflow.