A mobile device is coupled to a computer system configured to access media content sources and play media content items provided thereby on a media device. The mobile device receives a first control specification that includes a plurality of first information items each associated with one of the media content sources and a first action definition. The first information items are concurrently displayed on a remote control user interface of the mobile device. In accordance with a selection of one of the first information items corresponding to a first content source, the mobile device transmits a command of a first action definition corresponding to the selected first information item to the computer system, and receives a second control specification that includes a plurality of second information items. Each second information item is associated with a respective content item provided by the first content source and a second action definition.