| ”Customer ID is required” | Add a shopifyCustomerId field with a valid string value |
| ”Customer ID must be a Shopify GID” | Use the format gid://shopify/Customer/123456789 |
| ”Product variant ID is required” | Add a productVariantId field with a valid string value |
| ”Product variant ID must be a Shopify GID” | Use the format gid://shopify/ProductVariant/123456789 |
| ”Payment reference is required” | Add a paymentReference object with gateway, customerId, and paymentMethodId |
| ”Unsupported gateway” | Use one of: stripe, braintree, authorize_net, paypal |
| ”Recurring price must be a positive number” | Provide a numeric string greater than zero (e.g., "29.99") |
| “Currency code is required” | Add an ISO 4217 currency code (e.g., "EUR", "USD") |
| “Billing interval is not supported” | Use WEEK, MONTH, or YEAR |
| ”Billing interval count must be at least 1” | Provide a number >= 1 |
| ”Next billing date must be a valid date” | Use ISO date format (e.g., "2026-04-01") |
| “Delivery address is required” | Add a deliveryAddress object with shipping details |
| ”Status is not supported” | Use ACTIVE or PAUSED |