Lists multiple specific concrete actions: 'GLSL, ShaderMaterial, uniforms, custom effects' and 'modifying vertices, writing fragment shaders, extending built-in materials' - these are concrete, actionable capabilities.

Clearly answers both what ('Three.js shaders - GLSL, ShaderMaterial, uniforms, custom effects') AND when ('Use when creating custom visual effects, modifying vertices, writing fragment shaders, or extending built-in materials') with explicit trigger guidance.

Excellent coverage of natural terms users would say: 'Three.js', 'shaders', 'GLSL', 'ShaderMaterial', 'uniforms', 'custom effects', 'vertices', 'fragment shaders', 'materials' - these are exactly what developers would mention when needing shader help.

Highly distinctive niche - Three.js shaders and GLSL are very specific to WebGL/3D graphics programming. Unlikely to conflict with general JavaScript, CSS, or other visual skills due to the technical specificity of shader terminology.

The skill is lean and efficient, presenting code examples without unnecessary explanations of basic concepts. Every section provides actionable code snippets without verbose preambles about what shaders are or how GLSL works.

Fully executable code examples throughout - from basic ShaderMaterial setup to advanced patterns like Fresnel effects, dissolve, and instancing. All code is copy-paste ready with complete shader strings and proper Three.js integration.

For a reference-style skill covering shader patterns, the organization is clear. Each section builds logically from basics (Quick Start) to advanced topics (extending materials, debugging). The debugging section provides explicit validation approaches for shader development.

Well-organized with clear sections progressing from quick start to advanced topics. Appropriate cross-references to related skills (threejs-materials, threejs-postprocessing, threejs-textures) at the end. Content is appropriately contained without excessive nesting.