Conciseness

The body is lean — tables, code, and bullets with essentially no prose padding — and every section carries project-specific values (320/768/1024px breakpoints, 48px touch targets, <100KB budgets). It falls short of 5 only because the opening line and parts of the CSS example restate standard mobile-first mechanics (basic min-width media query syntax) that Claude already knows; it is well above 3 since nothing is padded or over-explained.

Actionability

The CSS is complete and copy-paste ready (base styles, nav toggle, layered min-width queries), and the touch-target and performance sections give exact executable values ("min-height: 48px", "<100KB gzipped"). Specific examples cover the common cases, matching the top anchor.

Workflow Clarity

This is a simple single-purpose skill and the single action is unambiguous: the CSS example explicitly demonstrates the layered sequence ("Base styles (mobile)" → "Tablet and up" → "Desktop") and "Start design at 320px width" plus "Test on real devices" give direction and a check step. Per the simple-skill guideline this warrants 5; there are no destructive or batch operations that would impose a validation cap.

Progressive Disclosure

Sections are well-organized with clear headers and no content that belongs in a separate file is inlined (verified: no references/, scripts/, or assets/ bundle exists, and the body references no external paths). It misses 5 only because at ~100 lines it exceeds the under-50-lines simple-skill threshold and all material lives in one file; structure is good but the skill is a single monolithic reference rather than an overview with signaled deeper material.

Specificity

"Designs responsive interfaces starting from mobile screens with progressive enhancement for larger devices" names the domain and 1-2 concrete actions (designing mobile-first, progressive enhancement), matching the 'Processes PDF files and extracts content' level rather than a list of several specific actions. It is not a 4 because it doesn't enumerate multiple specific capabilities (e.g., fluid grids, responsive images, breakpoint scaffolding); it is above 2 because the actions stated are more concrete than a bare domain mention.

Completeness

It explicitly answers 'what' ("Designs responsive interfaces starting from mobile screens with progressive enhancement") and 'when' with concrete trigger phrases ("Use when building responsive websites, optimizing for mobile users, or implementing adaptive layouts"), mirroring the top anchor's structure of capability statement plus explicit multi-trigger 'Use when' clause. Not a 4 because the 'when' clause is already explicit and specific rather than needing more detail.

Trigger Term Quality

"building responsive websites, optimizing for mobile users, or implementing adaptive layouts" provides good natural keyword coverage with phrasing users would actually say. Not a 5 because common variations users might use are missing — e.g., "mobile-first", "media queries", "breakpoints", "make it responsive".

Distinctiveness Conflict Risk

The mobile-first/progressive-enhancement framing carves a clear niche with distinct triggers, distinguishable from generic CSS or general design skills. Not a 5 because "responsive websites" and "adaptive layouts" are broad phrases that could overlap with a general responsive-design or CSS skill; not a 3 because the explicit mobile-first positioning meaningfully narrows the trigger space.