Wix Service Plugin (SPI) Builder

Creates service plugin extensions for Wix CLI applications. Service plugins are a set of APIs defined by Wix that you can use to inject custom logic into the existing backend flows of Wix business solutions or to introduce entirely new flows to Wix sites.

When you implement a service plugin, Wix calls your custom functions during specific flows. Common use cases include eCommerce customization (shipping, fees, taxes, validations) and Bookings customization (staff sorting), but service plugins can extend any Wix business solution that exposes SPIs.

Quick Start Checklist

Follow these steps in order when creating a service plugin:

1. Read the reference doc for your SPI type, then STOP and call ReadFullDocsMethodSchema with the docs URL from the reference to get the exact request/response types — DO NOT write any code until you have the schema
2. Create plugin folder: src/extensions/backend/service-plugins/<service-type>/<plugin-name>/
3. Create plugin.ts with correct imports and provideHandlers() call
4. Implement all required handler functions with complete business logic
5. Create extensions.ts with appropriate builder method and unique UUID
6. Update src/extensions.ts to import and use the new extension
7. Run npx tsc --noEmit to verify TypeScript compiles
8. Run npx wix build to verify build succeeds
9. Test by triggering the relevant site action (e.g., add to cart for fees)