The body is dense with actionable API guidance organized into tight bullet sections and does not explain concepts Claude already knows (no 'what SwiftUI is' or 'what a window is' padding). Every section earns its place, matching the 'lean and efficient' anchor rather than the 'mostly efficient but could be tightened' level.

Concrete Swift snippets and named modifiers (.toolbar(removing: .title), .containerBackground(.thickMaterial, for: .window), .windowMinimizeBehavior(.disabled), WindowDragGesture(), .defaultWindowPlacement, etc.) give copy-paste-ready guidance. The only abstractions are trivial math helpers in the placement snippet, which does not drop it to the pseudocode anchor.

The numbered Workflow includes an explicit verification checkpoint (step 6: build and launch with build-run-debug to verify) and an escalation/fallback path (step 7: switch to appkit-interop), plus a separate Review Checklist. This matches the 'clear sequence with explicit validation steps and checklists' anchor.

The skill is a single well-organized file with clearly labeled sections and no nested references; navigation is easy and the 'When To Use Other Skills' section signals sibling-skill routing. With no need for external bundle files, the well-organized structure meets the top anchor.

Lists many concrete actions (styling/hiding toolbars and titles, extending drag regions, replacing backgrounds with materials, disabling minimize/restoration, setting placement, creating borderless windows, tuning launch behavior) and names the specific APIs (Window, WindowGroup, WindowDragGesture). This is a clear match for 'lists multiple specific concrete actions' and not the level below, which only names a domain and some actions.

It states what the skill does ('Customize macOS 15+ SwiftUI windows and scene behavior...') and gives an explicit 'Use when...' clause enumerating triggers, answering both what and when. This matches the top anchor and exceeds the 'has what, when missing or implied' level.

Phrases like 'window toolbars and titles', 'drag regions', 'utility windows', 'window placement', 'borderless windows', and 'launch behavior' are terms a macOS SwiftUI developer would naturally say. Coverage of natural terms is good rather than partial, so it is above the 'some relevant keywords' anchor.

The niche is narrow (macOS 15+ SwiftUI window/scene customization) with distinct triggers unlikely to fire for unrelated skills, and the body further delineates sibling skills. It is clearly above the 'somewhat specific but could overlap' anchor.