Conciseness

Lean and dense — every section carries non-obvious, Apple-specific facts ("Nonce must equal SHA256(authData || SHA256(challenge))", the appattest-environment entitlement key) rather than restating concepts Claude already knows. Not 4: there is no over-explanation to trim; the brief stage list and security-boundary note each earn their tokens.

Actionability

Concrete, realistic Swift for token generation, key generation/attestation, and assertion signing, plus specific error-recovery behavior and header names ("X-App-Attest-Assertion"). Not 5: snippets are not fully copy-paste ready — `import CryptoKit` is never shown and `fetchAttestationChallenge()`/`sendAttestationToServer()` are undefined app-specific glue, which are minor gaps per the anchor.

Workflow Clarity

The three-stage model (key generation, attestation, assertion) is clearly sequenced with a numbered attestation flow, error-recovery feedback loops ("Retry attestation with the same keyId ... using exponential backoff" vs. regenerate on .invalidKey), and a review checklist. Not 4: validation checkpoints and retry/regenerate loops are explicit, not implicit; this is not a destructive/batch operation so no cap applies.

Progressive Disclosure

The body is an overview plus client-side essentials; server verification algorithms, retry strategies, and the integration manager are correctly split into a single real, one-level-deep bundle file (references/device-integrity-patterns.md) that is clearly signaled and described in the References section. Not 4: the split placement and navigation (Contents list, labeled reference) leave no organization gaps.

Specificity

Enumerates multiple concrete capabilities — "App Attest key generation and attestation, request assertions, server verification, compromised-device signals, app authenticity, replay resistance" — comprehensively covering the skill's surface. Not 4: the coverage has no significant gaps relative to what the skill actually contains.

Completeness

Explicitly answers both: what ("Protects apps and APIs with DeviceCheck and App Attest") and when ("Use for per-device fraud state, ... or sensitive endpoint protection") with concrete trigger phrases. Not 4: the when-clause is explicit and specific, not merely present.

Trigger Term Quality

Good natural-term coverage ("per-device fraud state", "app authenticity", "replay resistance", "sensitive endpoint protection") that matches how users phrase these needs. Not 5: a few natural variations are missing — no "iOS"/"Apple" platform qualifiers and no "app integrity" phrasing, so users who ask in platform terms rather than framework names may not trigger it.

Distinctiveness Conflict Risk

"DeviceCheck and App Attest" are unambiguous Apple framework names establishing a clear niche with minimal overlap risk; trigger terms like "App Attest key generation" would not fire a generic security or fraud skill. Not 4: no closely related skill in this space would plausibly collide with these triggers.