Conciseness

Nearly every sentence carries non-obvious domain facts (retry schedule '5, 10, 20, 40, and 80 minutes', grace-period vs account-hold semantics, store-specific quirks) and it assumes Kotlin/Ktor competence without tutorializing. A few long, clause-heavy sentences (e.g., the anonymous-purchase/login paragraph) could be tightened, so it sits just below the lean anchor 5.

Actionability

Fully executable Ktor code: constant-time Authorization compare, HMAC-SHA256 verification with timestamp tolerance, unknown-key-tolerant JSON config, serializable event models, dedup via insertIfAbsent, and a dispatch skeleton — plus an exact behavioral spec for syncFromRevenueCat and three realistic sample payloads. Copy-paste ready with the common cases covered.

Workflow Clarity

Sequenced as Discover → Plan → Execute with a per-event-type decision table, and closed by a 13-item Verification Checklist that acts as explicit validation checkpoints (401 on bad auth, replay no-op, retried EXPIRATION after resubscription leaves access on). Error-recovery feedback loops are spelled out (rollback of the event-ID insert on failed re-read, skip writes from stale request_date_ms, re-read before denying expired access), matching the anchor-5 pattern.

Progressive Disclosure

No bundle files exist, and the single ~300-line file is well organized with clear phase and section headers; the event-type table is decision-critical and reasonably inline, and the one external link ('Full chapter') is clearly signaled. It sits between anchors 3 and 4 — above the midpoint because nothing is buried and structure is good, but the sample-payload section and parts of the event catalog could be split into reference files to shrink the always-loaded SKILL.md.

Specificity

Enumerates concrete, field-level actions across the whole pipeline: 'authenticating requests (Authorization header, optional HMAC signing)', 'parsing the normalized event schema without breaking on new fields', 'idempotency via the event id field', 'every event type', and 'taking access from a re-read of the customer'. This is comprehensive coverage matching the anchor-5 example, not just several actions with gaps.

Completeness

Explicitly answers both: the opening 'Use this skill when consuming RevenueCat webhooks on your backend' gives a concrete trigger, and the rest enumerates exactly what the skill covers (authentication, schema parsing, idempotency, event types, access re-read). Not 4 because the 'when' is explicit and specific, not merely present.

Trigger Term Quality

Good natural-term coverage: 'RevenueCat webhooks', 'backend', 'cancellation', 'expiration', 'renewal', 'idempotency', 'event type' — phrases a user with this need would actually say. A few natural terms are missing, notably 'entitlement(s)' and 'subscription', which users commonly name when troubleshooting access, so it falls short of the comprehensive anchor 5.

Distinctiveness Conflict Risk

'RevenueCat webhooks on your backend' names a clear niche with distinct triggers (RevenueCat, webhook event types, entitlement access); no realistic overlap with other skills, matching the clear-niche anchor.