Gmail action buttons

Question

Recently Gmail started showing "action" buttons next to emails that have links to trigger actions on certain third-party sites. For instance:

At first, I only noticed it with emails from Amazon, but it appears that emails from arbitrary sites occasionally have that, too.

How is Gmail able to tell?

This is so I can send emails that have such action buttons as well to my users (in case it's something special with the headers or such).

Answer 1

You can use Schemas, here's Google's documentation about it.

And here's the blog-post with the introduction of it.