A control application of a media playback system controls playback of media content by a media playback system. The application receives, from a media streaming service, a page object that identifies (i) a page format identifier, (ii) page content data, (iii) a set of page elements, and (iv) a respective element format identifier for each page element of the set of page elements. The application determines a first set of formatting rules using the page format identifier and displays a corresponding page that includes the page content data formatted using the first set of formatting rules. The application asynchronously receives media content data identifying media content available for streaming. Based on a respective element format identifier of the page element associated with the media content data, the application determines a second set of formatting rules, which the application uses to update the displayed page to display the media content data.