Conciseness

The body is a lean ~145-line index: each section is a one-line pointer plus 3-5 topic bullets ("See [rsc-boundaries.md](references/rsc-boundaries.md) for: Async client component detection..."). No concept explanations Claude already knows, no padding; the one-line intros ("Next.js 15+ async API changes.") earn their place as version context. It is not below 5 — nothing here can be cut without losing discovery value.

Actionability

Pointers are concrete (exact file paths with topic bullets), but the body itself contains no executable guidance — no code, commands, or rules; the directive "Apply these rules when writing or reviewing Next.js code" defers all actual rules to the references. This fits the 3 anchor (some concrete guidance but incomplete / missing key details) rather than 4, since even the most common cases (e.g. 'use client' placement, async params) have no inline example; it is above 2 because the navigation it does give is specific and immediately followable.

Workflow Clarity

For a reference-lookup skill the single action is unambiguous (match the concern, read the named file), and the 18 concern-labeled sections make selection easy. Not a 5: with 18 parallel topics there is no guidance on priority or which file to consult when multiple apply, and no verification step for applying rules during code review; not a 3 because the structure itself is coherent and complete with no gaps in the lookup flow.

Progressive Disclosure

Textbook one-level-deep structure: every section links a real file in references/ (all 19 linked paths verified to exist, no nested .md chains), each clearly signaled with topic bullets. It falls short of 5 because the bundle contains references/app-router-files.md, which is never linked from the body — an orphaned file that hurts discoverability against the 'easy navigation' anchor.

Specificity

"building, debugging, or architecting Next.js applications" names three concrete actions, and the enumeration "routing, Server Components, Server Actions, Cache Components, layouts, middleware/proxy, data fetching, rendering strategies, and deployment on Vercel" gives broad, specific coverage. Not a 5 because the head noun "expert guidance" is abstract — capability is conveyed as a topic list rather than multiple concrete operations like the 5-anchor examples ("Extract text... fill forms, merge documents").

Completeness

Explicitly answers both: what ("Next.js App Router expert guidance" with a concrete topic inventory) and when ("Use when building, debugging, or architecting Next.js applications"), with concrete trigger phrases. This matches the 5-anchor pattern (what + explicit 'Use when...' with triggers); it is not a 4 because the 'when' clause is specific and multi-scenario, not merely present.

Trigger Term Quality

Strong natural phrases users would say — "Next.js", "App Router", "Server Components", "Server Actions", "layouts", "data fetching", "Vercel". A few natural terms are missing (e.g. "use client", "pages router", file extensions like .tsx), so it falls short of the comprehensive-with-synonyms 5 anchor.

Distinctiveness Conflict Risk

"Next.js App Router" is a clear, well-named niche with distinct framework-specific triggers (Server Actions, Cache Components, middleware/proxy, Vercel), so overlap with generic React or web-dev skills is minimal.