Conciseness

The body is dense with non-obvious, skill-specific guidance (divergence rules, the isolated prototype surface path, 100+/session flip frequency justifying no swap animation) and explains nothing Claude already knows. Minor trimmable redundancy remains — e.g. the Tone section re-states Phase 5's table contract ("one line on when it wins, one on what it costs"), and the Operating Posture explains the divergence rationale twice — so it fits anchor 4 rather than anchor 5's 'every token earns its place'.

Actionability

Much is concrete and executable: exact paths (".playwright-tmp/prototypes/<slug>/"), default variant counts (3, cap 5), concrete invocation syntax ("<description> x5", "riff <variant>", "keep <variant>, leave the picker"), and specific motion standards. But the core deliverable — the picker — is specified only as "Its exact markup, styles, and behavior are specified in [PICKER.md](PICKER.md) — copy them verbatim", and PICKER.md is absent from the bundle, leaving the central artifact unbuildable. That is a missing key detail, matching anchor 3 rather than 4.

Workflow Clarity

Six phases are clearly sequenced with explicit checkpoints: completion criteria in Phase 3 ("every variant has a name and a stated axis") and Phase 5 ("no console errors; the table names each variant's tradeoff"), plus a Phase 5 verification pass ("flip through all of them yourself"). The destructive operation (deleting the prototype surface, Hard Rule 5) is gated behind explicit user selection. It falls short of anchor 5 because there is no error-recovery loop when Phase 5 verification fails, and execution depends on the missing PICKER.md.

Progressive Disclosure

Structure is good: a sectioned overview (posture, hard rules, phases, invocation table) with a well-signaled, one-level-deep reference to PICKER.md ("load it now and build exactly that"). However, the referenced file does not exist in the bundle — the only external reference is dangling, so the disclosure structure does not actually hold, matching anchor 3's 'could be better organized' rather than anchor 4's 'references mostly clear'.

Specificity

The description lists several concrete actions — "Build multiple genuinely different versions of a UI piece", "rendered behind a visual picker", "flip through them live", "promote the one that feels right" — which fits anchor 4 with minor coverage gaps (no mention of variant counts, riff/keep rounds, or cleanup). However, it uses second person ("a UI piece you describe"), which the rubric penalizes by one point, bringing it to anchor 3.

Completeness

The 'what' is fully explicit (build divergent variants of a described UI piece behind a live picker; promote the winner). The 'when' is explicitly stated — "Only runs when explicitly invoked; it does not trigger on its own" — which is real trigger guidance (consistent with disable-model-invocation), but it is purely an exclusion with no positive use-case trigger phrases, so it falls between anchor 3 (when weakly implied) and anchor 4 (when present but could be more specific).

Trigger Term Quality

Natural phrases a user would say are present: "different versions", "visual picker", "flip through", "promote", "UI piece". It misses common synonyms like "prototype", "mockup", "design variations", or "directions", so it does not reach anchor 5's comprehensive synonym coverage, but it is noticeably above the midpoint.

Distinctiveness Conflict Risk

A clear niche — divergent variant generation behind a live visual picker — that is distinguishable from generic UI-building skills, and the "does not trigger on its own" note eliminates auto-trigger conflict entirely. It stops short of anchor 5 because the description itself doesn't positively disambiguate against closely related UI-design skills (that boundary work lives in the body, not the description).