@tstarling asked that we include an indicator for the result media type in the endpoints. I think that's fine. I'd suggest we append /json to the URL patterns, as follows:
/page/{title}/history/json /revision/{id}/compare/{other}/json /revision/{id}/json
There are other mechanisms for doing this; some APIs do ".json" as if there is a virtual JSON file on a server being shared. I think it's OK, too.