Conciseness

The body is mostly on-topic guidance with no concept explanations Claude already knows, but it can be tightened: the "Use When" section repeats the frontmatter description word-for-word, and "Tuning knobs" restates parameters already covered in "Implementation guidance" (fold count/density, drift, color, softness). Anchor 3 (mostly efficient, some unnecessary content) fits better than 4 given this duplication, but it is far from the padded verbosity of anchor 2.

Actionability

Guidance is qualitatively concrete ("screen or additive-style blending", "vertical gradients that fade at the top and intensify toward the bottom", "subtle radial glow overlay"), but there is no code, no concrete parameter values (fold count, drift speed, gradient stops, canvas setup), and no minimal snippet to start from — matching anchor 3's "some concrete guidance but incomplete; missing key details". It is above anchor 2 because the visual recipe is specific enough to act on, and below anchor 4 because nothing is executable or copy-paste ready.

Workflow Clarity

The "## Workflow" section is present but completely empty, and the remaining content is organized by aspect rather than as a buildable sequence (layer order, when to add the radial overlay, how to verify the result). This is a simple single-purpose skill where 5 is possible if the single action is unambiguous, but the dangling empty Workflow header and absence of any ordered steps or verification check (e.g., visually confirm focal glow, check performance/fps) keep it at 3.

Progressive Disclosure

The body is ~38 lines with no bundle files (references/, scripts/, assets/ do not exist) and no external references, yet everything needed for this single-purpose visual skill is inlined under clear, well-labeled sections (Scope, Visual target, Implementation guidance, Tuning knobs, Avoid). Per the rubric's simple-skill guidance, an under-50-line skill with no need for external references scores 5 with well-organized sections, which this has.

Specificity

"Create a dark atmospheric background with drifting vertical light folds, screen-blended glow, and a concentrated luminous corner or lower-edge bloom" names the domain and several concrete visual features (vertical folds, screen blending, corner bloom). It falls just below anchor 5 because it covers a single action and its attributes rather than multiple comprehensive capabilities, but is clearly above anchor 3's minimal action list.

Completeness

The "what" is clearly stated (create an atmospheric background with specific visual characteristics), but there is no "Use when..." clause or equivalent explicit trigger guidance, which caps completeness at 3 per the rubric guidelines. Not score 4 because the "when" is entirely absent rather than merely under-specified.

Trigger Term Quality

Terms like "dark atmospheric background", "glow", and "bloom" are plausible user phrasings, but common variations a user would actually say are missing (e.g., "ambient background", "hero background", "light rays/curtains", "WebGL/canvas background"). Not score 2 because the keywords present are relevant and reasonably natural, not generic filler.

Distinctiveness Conflict Risk

"Drifting vertical light folds, screen-blended glow, and a concentrated luminous corner or lower-edge bloom" carves out a fairly specific visual niche unlikely to fire for unrelated skills, with only minor overlap risk with generic gradient/background or particle-effect skills. Not score 5 because the opening phrase "Create a dark atmospheric background" is broad enough that it could collide with general background-generation skills.