Shopify Functions

This is the official Shopify skill for building Functions, the backend customization layer that lets you modify discounts, payments, delivery options, cart validation, and fulfillment logic. It enforces a strict workflow: search the docs first, write your code, then validate before returning anything to the user. The skill defaults to Rust unless you specify JavaScript or TypeScript, and it knows the difference between current APIs (like the unified Discount function) and deprecated ones (the old order/product/shipping discount functions). One thing to know: Functions are pure, meaning no network access, no filesystem, no random numbers in the run targets. If you're customizing Shopify checkout or cart behavior beyond what apps can do, this is your entry point.