The response payload for ui.done and ui.launchActivity is limited by the two properties: success - the boolean flag; and details - a boolean description. This seems to be very limiting and may not allow to handle the response with sufficient flexibility as the receiving application will only know that the request has failed but would not be able to get the soort of problem encountered and thus handle it accordingly in its logics. So using a result code to communicate the result type could potentially allow for more sophisticated application logics.