The full list of available APIs is available on the developer page here: https://developer.surveymonkey.com/ There is no export function for any files, the only methods supported return JSON data (as you said: via get_responses). It is an often requested feature and it has been noted there is a lot of demand for it.

Context: Stack Overflow question (score 3, has accepted answer): Is it possible to export a csv or excel file through the SurveyMonkey API? Or is it necessary to page through the json get_responses and compile that list manually? Since you can export excel and csv reports through in the SurveyMonkey interface, it would be nice to have that functionality in the API.