Looking for guidelines for Creating Gmail Summary Cards for Order Emails

I'm looking for publicly known guidelines or specifications that can help us ensure that Gmail generates summary cards for our order-related emails. Our business sends out emails containing order details and payment options, but Gmail doesn’t seem to create those nice summary cards for them.

Here is a link explaining Gmail summary cards: Gmail Summary Cards.

Are there specific schema or markup guidelines that we should follow to enable Gmail summary cards? Is there any recommended best practice for formatting order emails to increase the likelihood of summary cards being displayed?

Summary cards example:

Yes, this feature is similar to Gmail's "Highlights" feature, so adding structured data to your emails should help Google understand its content and surface your email's data in the new "Summary Card" format.

See the Gmail Highlights documentation for further details. Orders are already supported, as detailed here:

Use order markup in emails that include a receipt for purchases (digital or physical goods). The user will see chips above the email message with information about cost, estimated delivery, and an image of the purchased item.

Order Highlights also support Actions, including View Order action.

To learn more, see the order markup reference.

You can use Google's Email Markup Tester to validate your code.