Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add RevenueCat/play-billing-skills --skill plan-changesgit clone --depth 1 https://github.com/RevenueCat/play-billing-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/revenuecat/play-billing-skills/plan-changes)<a href="https://agentmods.dev/skills/revenuecat/play-billing-skills/plan-changes"><img src="https://agentmods.dev/badge/skills/revenuecat/play-billing-skills/plan-changes/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/revenuecat/play-billing-skills/plan-changes"><img src="https://agentmods.dev/badge/skills/revenuecat/play-billing-skills/plan-changes.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00084 | $0.02528 |
| Opus 5.5 | $0.00034 | $0.01011 |
| Sonnet 5.5 | $0.00017 | $0.00506 |
| Haiku 4.5 | $0.00008 | $0.00253 |
Grade A, and why
plan-changes scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 175 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Plan Changes: Upgrades, Downgrades, and Plan Switches
Plan changes on Google Play Billing Library (PBL) 9.x always mint a new purchase token. You pick a replacement mode that controls two things: when the user gets access to the new plan, and how Google handles the money between the old and new agreement. This skill walks you through selecting the correct mode and wiring it into BillingFlowParams.
Phase 1: Scope the Change
Before touching code, answer four questions about the requested switch:
- Direction: is this an upgrade (new plan costs more), a downgrade (new plan costs less), or a lateral switch (same price, different cadence)?
- Billing period: are you moving between plans with the same billing period (monthly to monthly) or across periods (monthly to annual, recurring to prepaid)?
- Promotional state: is the user currently inside a free trial or introductory price window that should survive the switch?
- Additivity: is the new SKU replacing the old subscription, or should it sit alongside the old one as an add on?
Write those four answers down. Every decision in Phase 2 follows directly from them.
You also need three inputs from the client at runtime:
oldPurchaseToken: the purchase token for the subscription the user is leaving.oldProductId: the product ID of the subscription being replaced (from the activePurchase.products), forSubscriptionProductReplacementParams.setOldProductId.ProductDetailsand offer token for the new plan, fetched throughqueryProductDetailsAsync.
If any is missing, stop and fetch it first. Launching the billing flow without a valid oldPurchaseToken produces a new standalone subscription when the target is a different subscription (within the same subscription, Play applies the base plan's default replacement mode).
Also confirm the current purchase is acknowledged (Purchase.isAcknowledged); Play blocks plan changes while it is pending acknowledgement. If the original purchase used setObfuscatedAccountId, pass the same value on the plan change BillingFlowParams.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 11d ago Changed · +5 lines · +15 tokens per session e7f2c3ac79b4
- 1mo ago First seen · 170 lines · 69 tokens per session scan A 0d27537b9706
plan-changes is a skill published in the GitHub repository RevenueCat/play-billing-skills (58 stars, last pushed 12d ago), licensed Apache-2.0. It adds 84 tokens to every session and 2,528 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
play-billing-library-version-upgrade
Use this skill when upgrading or migrating an Android project from any legacy Google Play Billing Library (PBL) version to the latest stable version of PBL.
asc-revenuecat-catalog-sync
Reconcile App Store Connect subscriptions and in-app purchases with RevenueCat products, entitlements, offerings, and packages using asc and RevenueCat MCP. Use when setting up or syncing subscription catalogs across ASC and RevenueCat.
axiom-implement-iap
Use when the user wants to add in-app purchases, implement StoreKit 2, or set up subscriptions.
google-play
Google Play Developer API (Android Publisher) integration with managed OAuth. Manage apps, subscriptions, in-app purchases, and reviews. Use this skill when users want to interact with Google Play Console programmatically. For other third party apps, use the api-gateway skill (https://clawhub.ai/byungkyu/api-gateway).
gplay-iap-setup
In-app products, subscriptions, base plans, and offers setup for Google Play monetization, including bulk-localizing subscription display names, descriptions, and benefits across all locales. Use when configuring in-app purchases or subscription products.
rc-revenuecat-api-quick-reference
Use this skill as a quick reference for the RevenueCat Android SDK 10.x and REST API. Covers SDK init, common Purchases calls, CustomerInfo / Offerings access patterns, and the most used REST endpoints.