Both Google and Microsoft have published their API design guidelines, which are very much RESTful. Both companies have applied their guidelines to broader set of products at very large scale. At least, we have not seen alternatives that would be applicable or scalable to companies at Google or Microsoft scale.

API design is like UI design or car design or clothes design. It is a form of craft, which does take time and skills. API design is for customers to have best experience, it was never meant to save time or work for the designers.

Disclosure: contributor of Google API Design Guide.