What problem does it solve? Adding PayPal as a payment method involves platform-specific configuration, server-side order creation and capture, webhook signature verification, and idempotency handling — mistakes in any of these cause duplicate charges, unfulfilled payments, or security holes. This Skill provides the complete implementation path for each platform. ## Core Features & Use Cases - Platform Setup Guides: Step-by-step PayPal configuration for Shopify, WooCommerce, and BigCommerce, including Venmo and Pay Later enablement. - Headless Integration: JavaScript SDK button rendering, Orders API v2 server-side order creation and capture, and OAuth token handling for custom storefronts. - Webhook Security: Signature verification, correct event selection (PAYMENT.CAPTURE.COMPLETED), and capture-ID-based idempotency to prevent duplicate orders. - Use Case: A React/Next.js storefront adds PayPal buttons that create orders server-side with idempotency keys, capture payments only after COMPLETED status, and process webhooks with verified signatures. ## Quick Start Use the paypal-integration skill to add PayPal Express Checkout buttons to my WooCommerce store with Pay Later messaging on product pages.