Public API does not have a mechanism to set HTTP caching headers - and no default values are set.
This is hugely important in modern web-application developer where the focus is on single-page apps making multiple requests to the same XHR call for data e.g. refreshing lists after an update - without refreshing the whole page.
Some browsers - all versions of IE from 6+ for example - aggressively cache XHR requests to the same URL. This means a modern single page application that makes multiple requests to the Alfresco public API will have to resort to hacks like adding nonce values to a URL to force the browser to re-query the data. Also, if the cache headers are not set correctly - proxy servers in the middle between Alfresco and a client could also aggressively cache identical URL requests.
I suggest finish the implementation to set a Cache object value and add an annotation for it to allow developers to set explicit values other than the default (which I suggest is set to "no-cache") for implementations that require it like say dated Content retrieval.