Conciseness

Every section opens with a concrete failure mode and resolves into a tight code snippet or a numeric dial table; nothing re-explains Three.js or basic concepts ('Float32BufferAttribute copies your array... Symptom: everything is correct, nothing moves'). Matches the 5 anchor 'lean and efficient; every token earns its place'; no section is trimmable without losing actionable content.

Actionability

Guidance is highly concrete — exact constants ('0.42 + near * 0.58', 'slant = base * v * v', 'dt / 24') and a storm-vs-rain dial table — but several snippets are fragments rather than copy-paste code: blizzardAt() elides its body ('... // smoothstep in, hold, out'), anchor() depends on undefined camAz/cam, and strike() references external sfx/pulses. This fits the 4 anchor 'mostly executable guidance; concrete code with minor gaps' rather than 5's 'fully executable, copy-paste ready'.

Workflow Clarity

Sections form a coherent build order and the closing 'What to check before you call it done' is an explicit per-feature validation checklist (watch a single drop, two minutes in snow, five clear-to-snow entries, profile the storm). However there is no ordered step sequence and no error-recovery feedback loop, so it sits at 4 ('clear sequence with most checkpoints present; minor validation gaps') rather than 5.

Progressive Disclosure

The body is a single self-contained file with clear, well-scoped section headers and no nested or buried references (no bundle files exist to reference). All content is appropriately inline, though at roughly 170 lines it is near the upper limit of what belongs in one file — good structure with minor organization headroom, matching the 4 anchor.

Specificity

The description enumerates six concrete capabilities ('rain anchored inside the frustum', 'storm that is the rain leaned on rather than a second system', 'lightning on its own light with thunder scheduled by distance', 'snow that blows up into blizzards and keeps settling until the ground goes white', 'wet ground with puddles and splashes', 'looping ambience that has no seam') — comprehensive coverage with no gaps, matching the 5 anchor. It uses imperative verb form rather than first/second person, so no voice penalty applies.

Completeness

Both halves are explicit: a detailed 'what' (all six weather capabilities) and a concrete trigger clause — 'Use for scene atmosphere, seasonal states, hero backdrops, or any world where clear/rain/storm/snow needs to be a control the viewer can turn.' This matches the 5 anchor with concrete trigger phrases; 4 would require a merely adequate 'when', which is not the case.

Trigger Term Quality

Natural terms a user would actually say are comprehensively covered: 'Three.js scene', 'weather', 'rain', 'storm', 'snow', 'lightning', 'thunder', 'scene atmosphere', 'hero backdrops', 'seasonal states'. No common variation a user would reach for is missing, matching the 5 anchor over the 4 ('a few natural terms missing').

Distinctiveness Conflict Risk

Clear niche — weather effects in Three.js scenes — with distinctive triggers (frustum-anchored rain, settled snow, seamless ambience) that no generic or adjacent skill would claim, matching the 5 anchor's 'clear niche with distinct triggers; minimal conflict risk'.