What problem does it solve? Building payment and subscription systems from scratch involves complex decisions across providers, webhook security, subscription state management, and regional legal compliance. This Skill generates production-oriented payment integration code so you avoid common pitfalls like missing signature verification, non-idempotent webhooks, and broken subscription state transitions. ## Core Features & Use Cases - Provider Selection Guidance: A decision tree routes you to the right provider—RevenueCat for mobile subscriptions, Stripe for global web payments, PortOne for Korean 간편결제 (Toss/Kakao/Naver), or Paddle/Lemon Squeezy for merchant-of-record simplicity. - Complete Implementation Artifacts: Produces SQL schemas for subscriptions and payments, webhook handlers with HMAC signature verification and idempotency, a full subscription state machine (trialing → active → past_due → canceled), and sandbox test configurations. - Korea-Specific Compliance: Covers auto-renewal advance notice requirements, cash receipts/tax invoices, and the 7-day withdrawal rules under Korean e-commerce law. - Use Case: You are adding a paid tier to your SaaS. Ask for a Stripe subscription integration and receive the database schema, webhook handler with signature verification, dunning logic for failed payments, and a sandbox test checklist. ## Quick Start Ask the AI to implement a Stripe subscription system with webhook handling and a subscription state machine for your web app.
