Shopify Dev MCP and AI Toolkit: developing reviewed extensions

Shopify Dev MCP connects AI-assisted development tools with Shopify resources. Current documentation places it within Shopify AI Toolkit. It can help consult APIs, prepare code and validate it; it does not guarantee that an extension is production-ready after its first generated version.

For checkout, the first task is choosing the right technology. Displaying a block, validating a business rule and modifying a delivery option are different types of extension.

What the development environment provides

The official Shopify AI Toolkit guide is the starting point for installing and using the current tools. Avoid copying requirements from old versions or similarly named packages without checking that documentation.

The value lies in platform context: which surface is being developed, which API version applies and which references the assistant should use. A model with documentation can still misunderstand a requirement or suggest behaviour the API does not support.

Before requesting a Checkout UI extension

1. Describe what the buyer needs and at which point in the journey.
2. Define whether data is displayed, requested, saved or used to block an action.
3. Check which extension or function can implement that behaviour.
4. Verify the required plan, permissions and APIs.
5. Specify behaviour when data is missing or an external service fails.

The checkout technologies table helps distinguish the alternatives. Restrictions depend on the surface; not all checkout customisation is available on every plan.

Which checkout surfaces depend on Plus

Interface extensions in the information, shipping and payment steps require Shopify Plus. Thank-you and order-status extensions have different scope and availability. Verify the exact target before budgeting or developing.

A Checkout UI extension does not automatically replace server-side validation or a payment integration. Displaying a message about a rule does not ensure that the rule applies to every purchase journey.

Writing a useful request for the assistant

We need to collect an optional delivery reference on the checkout target supported by our plan. The field needs a translatable label, a length limit and error handling. Explain where the data is stored and which permissions it needs. Use the project's API version and validate the code before proposing it for review.

Add the app's real structure and relevant restrictions. Do not include credentials, customer data or secrets in a prompt unnecessarily. Test data and the specific error are usually enough to reproduce a fault.

A verifiable workflow

Do not request every behaviour in one generation. Check the minimum journey first and add rules incrementally. This makes it easier to identify which change introduces a fault.

Checkout-specific tests

Shopify provides an extension testing guide. Prepare scenarios for mobile, languages, empty fields, address changes and slow external services where they affect your implementation.

• The buyer can understand and use the control with a keyboard.
• The extension does not depend on data missing from some orders.
• Failures show a useful state without unnecessarily blocking a purchase.
• Data is saved in the intended place and reaches the system that needs it.
• Requested permissions match the actual scope.

What needs to remain maintainable

Document API version, dependencies, configuration and tests. Establish who will handle future changes and how the extension can be disabled during an incident. Initial time saved on writing is not worthwhile if nobody can maintain the result.

For storefront blocks, see AI-generated theme blocks. For platform changes and dependencies, the Shopify Plus technical migration guide offers a wider framework.

If you need to turn a checkout idea into a testable technical scope, we can help through Shopify consultancy.

Editorial review: the Migraciones.io team · 30 October 2026. Features, plans and availability are checked against the linked sources.