1. A computer-implemented method comprising: receiving speech data that encodes a candidate hotword spoken by a user; evaluating the speech data, or a transcription of the candidate hotword, using one or more predetermined criteria; generating, by one or more computers, a hotword suitability score for the candidate hotword based on evaluating the speech data, or a transcription of the candidate hotword, using the one or more predetermined criteria, wherein the hotword suitability score reflects a suitability of the candidate hotword for future use as a hotword; and providing a representation of the hotword suitability score for output to the user.