Google's John Mueller said he is not aware of Google working on or having any plans on working on an API for the structured data testing tool.
He asked the webmaster why and what would he use the API for? "I'm not aware of any such public plans," John said on Twitter about such a tool. "What would you want to do with such an API?" he added.
I'm not aware of any such public plans. What would you want to do with such an API?
— John ☆.o(≧▽≦)o.☆ (@JohnMu) November 17, 2017
I guess it could be used to find any structured data issues quickly for new pages or test pages you are about to release?
Why would you want an API for the structured data testing tool? Let John know.
Forum discussion at Twitter.