Question

Am I breaking any laws in the REST bible by returning application/octet-stream for my responses ? The REST endpoint receives 5 image urls.

{ "image1": "http://ww.o.com/1.gif",
  "image2": "http://www.foo.be/2.gif" }

and it will download these and return them as application/octet-stream.

CLARIFICATION: The client that invokes this REST interface is a mobile app. Every additional network connections made will reduce battery life by a few milliamps. I am forced to use REST because it is a company standard. If not, I will do my own binary protocol.

Answer 1

It is not so good, as the client will not know what to do with such binary data except of storing those bytes somewhere or sending them further to some other process (if this is all you need to do with your data, then it is fine).

You may take a look at multipart content types. IMO, a multipart message containing several image/gif parts would be a better alternative.