Conciseness

The body is 37 lines with zero padding: no explanations of concepts Claude already knows, just a compact "When to use this skill" bullet list and 15 one-line annotated reference links. Every token earns its place, matching anchor 5.

Actionability

The body contains no executable guidance at all — no quick-start example, no code, no concrete steps for building a component; it is purely an index ("[accessibility.mdx](./references/accessibility.mdx) - ARIA, keyboard navigation, WCAG compliance"). This sits between anchor 1 ("only describes rather than instructs") and anchor 3 ("some concrete guidance but incomplete") — the annotated links are high-level pointers but lack any specific steps to execute, fitting anchor 2.

Workflow Clarity

Building a component is inherently multi-step (define, type, style, test, document, publish), but the body provides no sequence, no indication of which reference to start with or in what order, and no validation checkpoints (e.g., accessibility testing). There is a rough topical organization but many gaps and no defined steps — anchor 2, not 3, because not even an implicit step order exists.

Progressive Disclosure

The body is a lean overview that delegates all detail to 15 one-level-deep reference files, all of which exist and contain substantive content, each signposted with a one-line description of its scope. This is exactly anchor 5's "clear overview with well-signaled one-level-deep references... easy navigation" — no inlined bulk content and no nested references.

Specificity

"Guide for building modern, accessible, and composable UI components" names the domain, and the trigger clause enumerates several concrete actions ("building new components, implementing accessibility, creating composable APIs, setting up design tokens, publishing to npm/registry, or writing component documentation"). It falls just below a 5 because the 'what' is a single high-level statement and body-covered topics like polymorphism/as-child and data attributes are absent — minor gaps, matching anchor 4 rather than 5.

Completeness

It explicitly answers both: the 'what' ("Guide for building modern, accessible, and composable UI components") and the 'when' with concrete trigger phrases ("Use when building new components, implementing accessibility, creating composable APIs, setting up design tokens, publishing to npm/registry, or writing component documentation"). This mirrors the anchor-5 example's structure (what statement + explicit 'Use when' with concrete triggers), and is above anchor 4 because the 'when' is explicit and specific, not merely present.

Trigger Term Quality

Natural phrases users would say are present ("building new components", "implementing accessibility", "design tokens", "publishing to npm", "component documentation"), giving good keyword coverage. A few natural terms are missing (e.g., "ARIA", "theming", "as-child", "polymorphic"), so it fits anchor 4 ("Good keyword coverage; a few natural terms missing") rather than the comprehensive synonym coverage of anchor 5.

Distinctiveness Conflict Risk

Triggers like "composable APIs", "design tokens", and "publishing to npm/registry" carve out a distinct component-building niche, but the broad "building new components" and "accessibility" triggers could overlap with general web-development or styling skills. Mostly distinct with minor overlap risk against closely related skills — anchor 4, not 5's 'minimal conflict risk'.