Thanks for posting your question about the Visa Checkout API. Just wondering, have you tried the API Explorer? In API Explorer, you can choose the Product API, Endpoint and Method to see the Request and Response. Here is the link to API Explorer - https://developer.visa.com/apiexplorer.
In addition to that, please navigate to the 'PDFs for Merchants Integrating with Visa Checkout' link below for downloadable documentation about Visa Checkout and how to integrate this API into your project.
Visa Checkout > PDFs for Merchants Integrating with Visa Checkout
Visa Checkout > PDFs for Merchants Integrating with Visa Checkout > Visa Checkout Integration Guide (Download files)
Hope that helps!
Visa Developer Team
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