Conciseness

Mostly lean, expert-level content with no basic-concept padding, but mode-validity rules are repeated across the prose, both tables, and the DEFERRED paragraph ('any other mode fails the purchase' appears four times), and version-sensitive details (SDK 10.x, Play Billing 8.3.0, deprecation since 10.3.0) sit inline rather than in a dedicated deprecated section. Efficient overall with trimmable redundancy — anchor 4, clearly above the noticeably-verbose 3 and below the every-token-earns-its-place 5.

Actionability

Fully executable copy-paste Kotlin covering the common case: PurchaseParams builder with oldProductId derivation from activeSubscriptions, replacementMode selection, awaitPurchase with PurchasesTransactionException and userCancelled handling, plus the required import and per-scenario mode tables. Covers the common cases with specific, runnable guidance.

Workflow Clarity

Four clearly sequenced phases with a preconditions checklist (including the DEFERRED RTDN requirement), a decision procedure for picking the mode, execution with explicit error handling and routing ('nothing active, route to purchase-flow instead'), and an explicit verification phase covering entitlement checks and the DEFERRED pending-switch caveat. The Common mistakes table adds a checklist, matching the anchor-5 pattern.

Progressive Disclosure

No bundle files exist, so all content is appropriately inline for a single-file skill, with well-organized sections, clearly signaled cross-skill links (rc-subscriptions, rc-purchase-flow, rc-error-handling), and a single external reference. At ~113 lines it exceeds the under-50-line simple-skill exception, and the reference structure is minimal, so it fits the good-structure-with-minor-gaps anchor rather than the well-signaled one-level-deep reference structure of a 5.

Specificity

Lists multiple concrete actions — 'implementing subscription upgrades, downgrades, and plan switches', 'picking a replacement mode', 'letting the SDK manage linkedPurchaseToken chaining' — and names the exact API type (StoreReplacementMode) with full domain scoping, matching the comprehensive anchor rather than the minor-gaps anchor.

Completeness

Explicitly answers both: an explicit 'Use this skill when implementing subscription upgrades, downgrades, and plan switches via RevenueCat on Android' trigger clause and a distinct 'Covers StoreReplacementMode, picking a replacement mode, and letting the SDK manage linkedPurchaseToken chaining' statement of what it does. The when-clause is concrete and specific, so the anchor-4 caveat ('when could be more explicit') does not apply.

Trigger Term Quality

Good natural terms ('subscription upgrades', 'downgrades', 'plan switches', 'RevenueCat', 'Android') but misses common variations users would say such as 'cross-grade', 'tier change', or 'switch plans'. Fits the good-coverage-with-a-few-missing-terms anchor, not the comprehensive synonym coverage of a 5.

Distinctiveness Conflict Risk

Clear niche — plan changes on an existing Google Play subscription via RevenueCat — with distinct triggers that separate it from sibling skills like a fresh-purchase flow. Minimal conflict risk with other skills.