Conciseness

The ~90-line body is dense with hard, Sirv-specific facts Claude does not already know - frame-count guidance ('24-36 frames... minimum 8, maximum 1000'), row/column naming semantics, option defaults, plan limits ('Free 0, Business 200, Enterprise 400'). The only orientation is a two-sentence intro explaining how Sirv assembles frames into a viewer, which is provider-specific rather than a concept Claude already knows, so this matches the 'lean and efficient; every token earns its place' anchor rather than anchor-4's trimmable over-explanation.

Actionability

Fully executable guidance: a copy-paste embed snippet (preconnect/dns-prefetch hints plus '<script src="https://scripts.sirv.com/sirvjs/v3/sirv.js">' and the 'class="Sirv"' div), exact filename patterns ('chair-01.jpg... chair-36.jpg', 'chair-r01-c01.jpg'), exact API endpoints ('POST /v2/files/video2spin', 'POST /v2/files/spin2video') with limits, and a complete options table with defaults and valid values. Specific examples cover the common cases (shoot/name/upload/embed/tune), matching the anchor-5 'copy-paste ready' example.

Workflow Clarity

The Default Workflow is a clear 6-step sequence with an embedded validation step ('6. Verify: drag rotation, zoom, mobile swipe vs page scroll, load performance, and CLS'), reinforced by a dedicated Verification checklist and a Red Flags section that maps failure symptoms to causes ('Filenames without a clean ascending sequence - frames assemble out of order or the .spin never generates'). Validation steps, a checklist, and error-recovery diagnostics are all present, matching anchor-5 rather than anchor-4's 'minor validation gaps'.

Progressive Disclosure

A single well-sectioned overview file with no bundle files to split; volatile specifics are delegated exactly one level deep and clearly signaled - current-spec details to official doc URLs (guarded by the 'Official Sources First' section), API auth/polling to '../sirv-api/SKILL.md', and gallery composition to '../sirv-media-viewer/SKILL.md'. This matches the 'well-signaled one-level-deep references' anchor; the sibling pointers are not part of this skill's bundle (no references/, scripts/, or assets/ exist) and cannot be verified in this review copy, but they are cross-skill pointers, clearly labeled with what each contains.

Specificity

Lists ~10 concrete actions phrased as specific verbs: 'Create and embed Sirv 360 spins', 'shooting or preparing spin frames, naming spin image sequences, configuring .spin files', 'building 3D multi-row spins, adding spin hotspots, converting video to spin or spin to video, or debugging a spin that won't rotate'. Comprehensive coverage of the domain with no vague filler; the bad-example style ('helps with media') is entirely absent, so this clearly matches the anchor-5 example rather than the 'several specific actions; minor gaps' anchor-4.

Completeness

Explicitly answers both questions: 'what' ('Create and embed Sirv 360 spins - interactive rotating product views' plus enumerated capabilities) and 'when' (an explicit 'Use when creating a 360 spin... or debugging...' clause followed by a 'Triggers on' list). This mirrors the anchor-5 example structure exactly; the anchor-3 cap for a missing 'Use when' clause does not apply.

Trigger Term Quality

Natural phrases users would actually say: '360 spin, product spin, 360 product photography, spin viewer, or rotating product view', plus domain synonyms (spin/rotating/360, viewer/view) and the '.spin' file extension in the capability list. This matches the comprehensive synonym-plus-extension coverage of the anchor-5 example ('PDF files, PDFs, forms, .pdf') rather than the 'a few natural terms missing' anchor-4.

Distinctiveness Conflict Risk

A clear niche (Sirv 360 spins specifically) with spin-specific triggers; a user asking about generic image galleries or video embedding would not match '360 spin'/'product spin'/'spin viewer'. Third-person voice throughout, so no voice penalty applies. Conflict risk with the sibling media-viewer skill is minimal because the triggers are scoped to spins, matching the 'clear niche with distinct triggers' anchor rather than anchor-4's 'minor overlap risk with closely related skills'.