Conciseness

The body is dense and terse - every section delivers version-specific facts, gotchas, and parameter semantics rather than concepts Claude already knows, and version-sensitive details are handled in the old-pattern/new-pattern 'Common Mistakes' format. The Quick Start includes standard renderer/camera boilerplate Claude already knows, which is trimmable, matching anchor 4 rather than the uniformly lean anchor 5.

Actionability

Every example is complete, executable JavaScript (Quick Start, ORM-packed PBR, toon gradient map, stencil masking, node materials) with comments that explain each parameter's range and meaning. Common cases are covered copy-paste ready, matching anchor 5.

Workflow Clarity

As a reference skill it has an unambiguous decision path: the Material Types Overview table with use-case and lighting columns routes to per-material sections, followed by shared properties, an impact-ordered performance list, and a wrong-to-right 'Common Mistakes' section that functions as error recovery. There are no explicit verification checkpoints (e.g. how to diagnose a washed-out or black render beyond the mistakes list), so it fits anchor 4; no risky batch operations exist that would cap it at 3.

Progressive Disclosure

Sections are clearly headed and the 'See Also' links to sibling skills, but there are no bundle files at all: the full ~500-line reference (all material APIs, the WebGPU/TSL guide, and 19 Common Mistakes entries) is inlined in SKILL.md. Content that could live in one-level-deep reference files is inline and references are absent rather than clearly signaled, matching anchor 3.

Specificity

Concrete actions ('Choosing and configuring') combined with comprehensive enumeration of every material family ('unlit, diffuse, specular, PBR, toon, point and line materials'), shared properties ('blending and stencil'), 'environment response', and 'the WebGPU node-material and TSL equivalents'. Coverage of the domain is comprehensive with no notable gaps, matching the anchor 5 example rather than anchor 4's 'minor gaps in coverage'.

Completeness

Both 'what' (choosing and configuring material types and shared properties) and an explicit 'when' ('Use when styling meshes or tuning material behavior') are present in third person. The 'when' clause is narrower than anchor 5's concrete multi-phrase triggers - it could name more specific scenarios (glass, fabric, brushed metal, cel shading) - fitting anchor 4.

Trigger Term Quality

Good natural keyword coverage: 'three.js materials', 'PBR', 'toon', 'blending', 'stencil', 'WebGPU', 'TSL', 'styling meshes', 'tuning material behavior'. A few natural terms users would say are missing (e.g. 'glass', 'transparent', 'shiny', 'metallic', 'cel shading'), so it matches anchor 4 rather than the comprehensive synonym coverage of anchor 5.

Distinctiveness Conflict Risk

'three.js materials' names a clear niche with distinct triggers; the enumerated scope (material types, shared properties, WebGPU/TSL equivalents) is unmistakably this skill's territory with minimal overlap risk, matching anchor 5. Adjacent topics (textures, lighting) are excluded from the description.