Conciseness

The body is largely lean and decision-focused (endpoint tables, key rules, 'what not to build'), with little padding and no explanation of generic concepts. Minor instances of over-explanation or time-sensitive detail keep it below level 5: the 'on by default since SDK 8.11.0' version pin is not confined to a deprecated/old-patterns note, though the deprecated 'duration' field is handled correctly.

Actionability

Concrete, near copy-paste-ready HTTP requests for the two main REST operations (GET subscriber with Authorization header, POST promotional with JSON body), a use-case-to-endpoint mapping table, and a Kotlin snippet. Minor gaps: the Kotlin example has no response handling, and the webhook use case is delegated to a sibling skill rather than shown, so it falls just short of fully covering the common cases at level 5.

Workflow Clarity

The Discovery → Plan → Execute phases are clearly sequenced and the discovery checklist acts as a pre-flight gate, but state-mutating operations (promotional grant and especially 'revoke_promotionals', which removes user access) have no verification step (e.g., re-reading the subscriber to confirm the entitlement changed). Per the rubric, missing validation for destructive operations caps workflow clarity at 3, which takes precedence over the otherwise clear sequencing.

Progressive Disclosure

Good single-file structure with clear section headers, a use-case table, and a one-level, clearly signaled handoff to the sibling rc-webhooks skill for webhook detail. It sits at level 4 rather than 5 because the body is over 50 lines, the ../rc-webhooks/ reference could not be verified against an actual bundle file, and a small API-reference section could live in a separate reference file.

Specificity

The description lists multiple concrete capabilities within its niche: 'read or update RevenueCat state on Android', 'v1 subscribers endpoint, grant/revoke entitlements, attributes', 'secret vs public SDK API key usage', and the receipt-verification boundary. Coverage is comprehensive for the domain, matching the level-5 anchor; it is not merely naming the domain with 1-2 actions (level 3) nor leaving minor gaps (level 4).

Completeness

It explicitly answers both questions: 'Use this skill when your backend needs to read or update RevenueCat state on Android' gives a concrete 'when', and 'Covers the RevenueCat REST API (v1 subscribers endpoint, grant/revoke entitlements, attributes)...' gives a clear 'what'. This mirrors the level-5 anchor's explicit what-and-when with trigger phrasing; level 4 would require the 'when' to be less explicit than it is here.

Trigger Term Quality

Natural trigger phrases like 'backend needs to read or update RevenueCat state', 'REST API', 'grant/revoke entitlements', and 'receipt verification backend' map well to what a user would say. A few natural terms are missing (e.g., 'webhooks', 'CustomerInfo', 'subscribers'), keeping it just below the comprehensive-synonym coverage of level 5.

Distinctiveness Conflict Risk

It carves out a clear niche (server-side RevenueCat state consumption on Android, explicitly excluding receipt verification and, by omission, webhooks) so it is unlikely to fire for the wrong skill. Conflict risk with generic backend or Android skills is minimal, matching the level-5 anchor.