In the Storefront API cart flow, use cartGiftCardCodesUpdate (check current API version availability) or note that gift card application may occur at the hosted checkout page rather than at the cart mutation level.
If gift card application is supported via cart mutations, pass the gift card code string to the relevant mutation and read cart.appliedGiftCards in the response.
If gift card application is only supported in Shopify's hosted checkout (not the cart API), redirect buyers to checkoutUrl with the cart and allow Shopify checkout to handle the gift card code entry field.
For headless checkouts using the checkout API (older pattern), use checkoutGiftCardsAppend with the checkout ID and an array of gift card codes.
Read appliedGiftCards.amountUsed and appliedGiftCards.balance to display remaining balance information to the buyer.
Consult current Shopify Storefront API docs and changelog for whether gift card mutations are available at the cart level or only at the checkout level in your target API version.
Known gotchas
Gift card code entry support varies by Storefront API version and checkout architecture (cart-based vs legacy checkout API); verify availability in the specific API version you are targeting before building a custom UI.
Applying a gift card to a cart does not guarantee it will fully cover the order total; always display remaining balance and the resulting amount due so buyers understand what payment method is still needed.
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claude mcp add --transport http waymark https://mcp.waymark.network/mcp