I would agree that creation of an API involves creative effort. I'd certainly agree that the original author should retain attribution rights, even if other parts of the bundle we call "copyright" are not reserved. There's also all the documentation of the API, which would of course be a separate matter—and a significant creative work of its own. (And an API means nothing without its documentation.)

However, I would argue that the bare listing of API endpoints/methods/names is like the numbers in a phone book -- a collection of facts, as in Feist Publications, Inc., v. Rural Telephone Service Co.. What are they facts about? The API documentation, of course. :-)