Mathoid currently exposes only one endpoint - POST / - which transforms the given TeX and returns all of the enabled formats. With its imminent integration with RESTBase (cf T102030 and T105975), it would be preferable to have a route that allows the client to specify the sought format and return only that. That can be as easy as creating the route /:format in Mathoid, checking the format and returning the render while setting the appropriate Content-Type header.