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 backendgit 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/backend)<a href="https://agentmods.dev/skills/revenuecat/play-billing-skills/backend"><img src="https://agentmods.dev/badge/skills/revenuecat/play-billing-skills/backend/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/backend"><img src="https://agentmods.dev/badge/skills/revenuecat/play-billing-skills/backend.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 | $0.00061 | $0.01393 |
| Opus 5.5 | $0.00024 | $0.00557 |
| Sonnet 5.5 | $0.00012 | $0.00279 |
| Haiku 4.5 | $0.00006 | $0.00139 |
Grade A, and why
backend 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.
This is a copy
100% identical to rc-backend — 31 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Backend Architecture with RevenueCat
You do not build a receipt verification server with RevenueCat. Your backend still has a role, but that role is consuming RevenueCat state, not validating Google Play purchase tokens.
Phase 1: Discovery
RevenueCat's backend is the receipt verification server. When the Android SDK posts a purchase token, RevenueCat's backend:
- Calls
purchases.subscriptionsv2.getorpurchases.products.getagainst the Google Play Developer API. - Validates the receipt is genuine and matches the expected product.
- Records the transaction in its database.
- Returns
CustomerInfoto the SDK.
Your Android app never calls the Google Play Developer API. Your server does not call it either.
Before writing any backend code, confirm these facts about your deployment:
- You have a RevenueCat project with an Android app configured.
- You have a secret API key from Project Settings to API Keys (not the public Android SDK key embedded in the app).
- You know which
app_user_idyour SDK uses (the same identifier your auth system uses). - You have decided whether the backend needs real time state (REST API) or event driven state (webhooks).
If your app only gates features inside the client, you may not need a backend component at all. RevenueCat verifies CustomerInfo server side before it reaches the SDK, and Trusted Entitlements (EntitlementVerificationMode.INFORMATIONAL, on by default since SDK 8.11.0) adds a response signature check you can read from EntitlementInfos.verification; it never blocks access by itself. Serve premium content from a server only when you can verify entitlement on the server.
Phase 2: Plan
Map each backend responsibility to a RevenueCat mechanism.
| Use case | Mechanism | Notes |
|---|---|---|
| React to purchase, renewal, cancellation | Webhook receiver | RevenueCat posts normalized events; your server updates its own DB. |
| Check current entitlement for a user | GET /v1/subscribers/{app_user_id} |
Secret API key in Authorization header. |
| Grant promotional access (support, refunds, comps) | POST /v1/subscribers/{app_user_id}/entitlements/{entitlement_id}/promotional |
Server side only. |
| Revoke promotional access | POST /v1/subscribers/{app_user_id}/entitlements/{entitlement_id}/revoke_promotionals |
Server side only. |
| Set subscriber attributes from server side data | POST /v1/subscribers/{app_user_id}/attributes |
Useful for CRM fields the SDK does not know. |
| Bulk data export | RevenueCat data export | Scheduled exports to your warehouse. |
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 · -15 lines f47d68d04706
- 1mo ago First seen · 137 lines · 61 tokens per session scan A cc2cd5902e54
backend is a skill published in the GitHub repository RevenueCat/play-billing-skills (58 stars, last pushed 12d ago), licensed Apache-2.0. It adds 61 tokens to every session and 1,393 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to rc-backend, differing in 31 lines, and is treated as a copy.
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