Conciseness

The body is lean and code-forward with no explanation of concepts Claude already knows, but the inline version pin "Targets Swift 6.4 / iOS 26+" is time-sensitive information not placed in a deprecated/old-patterns section, and a few explanatory sentences (e.g., the device-motion fusion rationale) could be trimmed.

Actionability

Provides executable, copy-paste-ready Swift snippets for accelerometer, device motion, pedometer, and activity updates, including availability guards; minor gaps remain in the altimeter/specialized section where APIs like startRelativeAltitudeUpdates are named but not demonstrated.

Workflow Clarity

Sections are logically sequenced (authorize, check availability, start, stop on background) and the Review Checklist supplies explicit verification checkpoints; the setup-to-usage flow is implied by section order rather than an explicit numbered sequence with error-recovery loops, keeping it below the top anchor.

Progressive Disclosure

The SKILL.md stays at overview level with a table of contents and delegates extended patterns via a clearly signaled, one-level-deep reference ("Extended patterns (SwiftUI integration, batched sensor manager, headphone motion, water submersion): references/motion-patterns.md"), which exists in the bundle and covers exactly those topics.

Specificity

Enumerates a comprehensive set of concrete sensor capabilities ("accelerometer, gyroscope, device motion, pedometer, activity recognition, altitude, headphone motion, workout motion, and submersion/depth data") but relies on a single verb ("Builds sensor workflows"), so it lists several specific capabilities with minor gaps rather than multiple distinct concrete actions.

Completeness

Explicitly answers both what ("Builds sensor workflows with Core Motion for accelerometer, gyroscope, device motion, pedometer...") and when ("Use for motion interaction, steps, activity classification, AirPods tracking, or watchOS depth features") with concrete trigger phrases, matching the top anchor exactly.

Trigger Term Quality

The trigger clause "Use for motion interaction, steps, activity classification, AirPods tracking, or watchOS depth features" contains natural phrases users would say, but common variations like "fitness tracking", "step count", "tilt", or "workout tracking" are missing.

Distinctiveness Conflict Risk

A clear Core Motion niche with distinct triggers like "AirPods tracking" and "watchOS depth features", but "steps" and "activity classification" carry minor overlap risk with a HealthKit or fitness-tracking skill.