1. A computer-implemented method comprising: receiving, by a speech recognition engine, data indicating a selection of a control for initiating speech recognition that is presented by a referring application; receiving, by a speech recognition engine, audio data that encodes an utterance; determining, by the speech recognition engine, that a transcription of the utterance includes one or more keywords associated with a command, and a pronoun; transmitting, from the speech recognition engine to the referring application, a disambiguation request, wherein the disambiguation request identifies the pronoun; receiving, by the speech recognition engine, a response to the disambiguation request from the referring application, wherein the response references an item of content identified by the application; and generating, by the speech recognition engine, the command using the keywords and the response.