Conciseness

The body is lean with no padding over concepts Claude already knows — the dual-grid concept explanation is two sentences of SpriteCook-specific framing, and practical notes are terse. The main trimmable redundancy is that the mask bit logic and the 17-entry `frameByMask` table appear twice (once in Mask Order, again inside `atlasCellForMask`/`dualGridMask` in Renderer Pseudocode), which is a minor but real duplication.

Actionability

Fully executable, copy-paste-ready TypeScript: `dualGridMask`, `atlasCellForMask`, `renderDualGrid`, and the `renderTwoSurfaceDualGrid` variant with the counter-surface base layer, plus the exact `frameByMask` lookup and atlas column/row math. Both common cases (single-surface and two-surface) are covered by concrete code.

Workflow Clarity

The single task is sequenced clearly (sample four cells → build mask → look up frame → draw → optional base layer) and there is an explicit validation cue ("Paint a test map before shipping a set. If the full tile (mask `15`) doesn't wrap, large filled areas show a visible checkerboard") plus failure-cause notes (e.g., transparent mask-0 areas without the base layer). It falls short of anchor 5's full validate→fix→retry feedback loop and checklists; rendering guidance is not a destructive/batch operation, so no cap applies.

Progressive Disclosure

No bundle files (references/, scripts/, assets/) exist and the skill is self-contained with well-organized, clearly headed sections (Concept, Mask Order, Renderer Pseudocode, Two-Surface Tilesets, Practical Notes). However, at ~155 lines it exceeds the under-50-line simple-skill threshold, so the inline full renderer implementations and lookup tables — content that could live in reference files — keep it at anchor 4 rather than 5.

Specificity

"Implementation guide for using SpriteCook top-down 15-piece tilesets with a dual-grid autotile renderer" and "map a 4x4 15-piece tileset image into terrain using SpriteCook's dual-grid mask system" name the domain and concrete, parameterized actions with only minor coverage gaps (e.g., two-surface sets and engine contexts unmentioned). This is above anchor 3's minimal 1-2 generic actions, but below anchor 5's comprehensive multi-action coverage.

Completeness

Explicitly answers both questions: the what ("Implementation guide for using SpriteCook top-down 15-piece tilesets with a dual-grid autotile renderer") and the when ("Use when explaining or coding how to map a 4x4 15-piece tileset image into terrain using SpriteCook's dual-grid mask system") with concrete trigger phrases. Not a 4 because the when-clause is specific and fully explicit rather than generic.

Trigger Term Quality

Strong natural keywords users would say in this domain: "SpriteCook", "tileset", "dual-grid", "autotile", "terrain", "15-piece". A few natural variations are missing (e.g., "tilemap"/"tile map", game-engine names), keeping it just below anchor 5's comprehensive synonym coverage.

Distinctiveness Conflict Risk

"SpriteCook top-down 15-piece tilesets" + "dual-grid autotile renderer" carves a clear, narrow niche, but a sibling generation skill exists (referenced in the body as `spritecook-generate-tilesets`) and the phrase "SpriteCook tileset" alone could plausibly trigger either, with no explicit disambiguation in the description itself. Fits anchor 4 (mostly distinct, minor overlap with a closely related skill) better than anchor 5.