Canva

Canva's API is modern and comprehensive, offering both Apps SDK and Connect APIs for different use cases.

OAuth2 authentication is well-implemented with extensive documentation and starter kits. The API covers design creation, asset management, brand templates, and collaboration features extensively. Sandbox environments and developer tools make testing straightforward. However, the breadth of features can be overwhelming, and some advanced features require app review.

It's excellent for design automation and creative workflows, with strong developer support and a large user base to target.