Conciseness

The one-line rule index assumes Claude's competence and avoids concept explanations, but it could be tightened: rule entries are duplicated across sections (e.g. 'geometry-merge-static' and 'geometry-instanced-mesh' appear under both §3 and §4), a 'Sources & Credits' block adds little actionable value, and the claim '120+ rules across 18 categories' contradicts the 23 categories listed in the table. Not 2 because there is no padded concept teaching; not 4 because the duplicates and inconsistencies are more than minor.

Actionability

Four complete, executable code blocks (import maps, disposal, TSL, mobile pixel-ratio) plus specific numeric targets ('under 100 draw calls', 'Limit to 3 or fewer active lights', 'Limit pixel ratio to 2') give real concrete guidance. However, most of the 120+ rules are direction-only one-liners ('Minimize vertex count', 'Consider interleaved buffers') whose executable detail is deferred to rule files that are not present, so the body alone is incomplete guidance.

Workflow Clarity

'When to Apply' and 'How to Use' sketch a rough usage pattern (find a category by priority, read the rule file), but there is no explicit sequence for applying the skill to a task (e.g. profile → pick category → apply → verify). This is a reference-index skill rather than a multi-step process, so no validation checkpoints are required, but the navigation-to-action sequence remains implicit.

Progressive Disclosure

The body is well organized as an index (priority table, prefixed rule IDs, one-level-deep references to rules/*.md), but every reference points to a 'rules/' directory that does not exist anywhere in the bundle (no rules/, references/, scripts/, or assets/ are present), leaving all navigation as dead ends. Not 4 because references that cannot be resolved are more than a minor organization gap.

Specificity

Lists several specific actions — 'writing, reviewing, or optimizing Three.js code' — anchored to a concrete domain with named subsystems (geometries, materials, textures, lighting, shaders), though 'best practices guidelines' is generic phrasing. Not 5 because 'performance optimization and best practices' is not as concrete as the actions in the top anchor; not 3 because it goes beyond naming the domain with 1–2 actions.

Completeness

Explicitly answers both what ('Three.js performance optimization and best practices guidelines') and when ('Use when writing, reviewing, or optimizing Three.js code', reinforced by an explicit trigger list), matching the top anchor with concrete trigger phrases.

Trigger Term Quality

Good natural keyword coverage ('3D scenes', 'WebGL/WebGPU rendering', 'geometries', 'materials', 'textures', 'lighting', 'shaders', 'TSL') that a user would plausibly say. Not 5 because common variations are missing — '3D models', 'WebXR', 'threejs', or asset extensions like '.gltf'/''.glb'.

Distinctiveness Conflict Risk

Clear Three.js niche with distinct, unambiguous trigger terms; very low risk of firing for the wrong skill.