There is no specific variables for checkout.html. All checkout functionality is handled via opening a new Tebex.js session. To start a new Checkout session, you should do the following:
GET
/checkout/ident
This endpoint will return an ident for the current basket, which is required by Tebex.js when launching a checkout modal.
Response
To learn how to add Tebex.js to your store, please view the associated documentation or view the demo over at https://js.tebex.io.