Conciseness

There is no padded prose — every line is code or terse comment — but large stretches duplicate API knowledge Claude already has, e.g., the ~120-line Math Utilities section listing "v.add(v2); v.sub(v2); ... THREE.MathUtils.clamp(value, min, max)" and Color constructor variants. This is 'mostly efficient but includes some unnecessary explanation or could be tightened' (3) rather than the 4-anchor's merely minor trimmable instances, given roughly a quarter of the file is standard-library reference.

Actionability

Everything is fully executable, copy-paste-ready code: the Quick Start is a complete runnable setup (scene, camera, renderer, mesh, lights, animation loop, resize handler), and every class section shows real constructor signatures with per-argument comments ("75, // Field of view (degrees)"). This matches the 5-anchor 'fully executable; copy-paste ready code or commands; specific examples cover the common cases'.

Workflow Clarity

The Quick Start gives a clear, correctly ordered setup sequence (scene → camera → renderer → mesh → light → animate → resize), and Common Patterns adds Clock-based animation and Proper Cleanup. Validation checkpoints are largely not applicable (non-destructive, non-batch work), but this is a broad multi-topic reference rather than a single unambiguous task, so it fits the 4-anchor 'clear sequence with most checkpoints present' rather than a 5.

Progressive Disclosure

There are no bundle files at all — the entire ~485-line body, including a full Core Classes and Math Utilities API reference, is inlined in SKILL.md. It is well-sectioned but 'content that should be separate is inline' with no offloading references (the "See Also" list points to sibling skills, not bundle files), matching the 3-anchor rather than the 4-anchor, which expects most bulk content placed in separate files.

Specificity

The description lists several specific capabilities — "scene setup, cameras, renderer, Object3D hierarchy, coordinate systems" — but these read as domain components rather than the verb-driven concrete actions of the 5-anchor ("fill forms, merge documents"), and capabilities the body actually covers (lights, math types) are not mentioned. It exceeds the 3-anchor's '1-2 concrete actions' but is not comprehensive action coverage, so 4.

Completeness

Both parts are explicit: the what ("Three.js scene setup, cameras, renderer, Object3D hierarchy, coordinate systems") and a concrete when ("Use when setting up 3D scenes, creating cameras, configuring renderers, managing object hierarchies, or working with transforms"). This mirrors the 5-anchor example's structure of explicit capability list plus enumerated concrete trigger phrases; the when-clause is specific, not the vague 'Use when working with documents' of lower anchors.

Trigger Term Quality

The trigger list "setting up 3D scenes, creating cameras, configuring renderers, managing object hierarchies, or working with transforms" contains natural phrases users would say, anchored by the distinctive keyword "Three.js". A few common natural terms are missing (e.g., "WebGL", "3D models", "Object3D", alternate "threejs" spelling), matching the 4-anchor 'good keyword coverage; a few natural terms missing' rather than the synonym- and extension-complete 5-anchor.

Distinctiveness Conflict Risk

"Three.js" plus the scoped fundamentals (scene setup, cameras, renderer, hierarchy, coordinates) carves a clear niche with distinct triggers, and the description deliberately avoids the territory of its named siblings (geometry creation, material types, lighting) except for one mild overlap in "working with transforms". This fits the 5-anchor 'clear niche with distinct triggers; minimal conflict risk' better than the 4-anchor's material overlap risk.