A method performed by a data processing apparatus, the method comprising: obtaining audio data representing a voice command spoken by a speaker; selecting a voice action based at least on a transcription of the audio data; selecting a service provider corresponding to the selected voice action from among a plurality of different service providers (240A, 240B, 240C, 240), wherein the selected service provider supports multiple voice actions requiring different types of data for authentication; determining an identity of the speaker using the audio data and a voiceprint for the speaker; identifying one or more types of data to provide to the selected service provider in connection with requests to perform the selected voice action, wherein the identified one or more types of data for authenticating the selected voice action are different to the data types that the selected service provider uses to perform authentication for at least one other voice action and wherein the identified one or more types of data comprise a data type that indicates whether the speaker's mobile computing device has been on a body since the mobile computing device was last unlocked and/or an input data type that indicates whether a speaker's mobile computing device is in short-range communication with a particular device; obtaining, without requiring the speaker to provide explicit information, one or more data values that correspond to the identified one or more types of data for authenticating the selected voice action; and providing, to the selected service provider, an indication of the identity of the speaker determined using the audio data and the voiceprint for the speaker, the obtained one or more data values, and a request to perform the selected voice action. obtaining audio data representing a voice command spoken by a speaker; selecting a voice action based at least on a transcription of the audio data; selecting a service provider corresponding to the selected voice action from among a plurality of different service providers (240A, 240B, 240C, 240), wherein the selected service provider supports multiple voice actions requiring different types of data for authentication; determining an identity of the speaker using the audio data and a voiceprint for the speaker; identifying one or more types of data to provide to the selected service provider in connection with requests to perform the selected voice action, wherein the identified one or more types of data for authenticating the selected voice action are different to the data types that the selected service provider uses to perform authentication for at least one other voice action and wherein the identified one or more types of data comprise a data type that indicates whether the speaker's mobile computing device has been on a body since the mobile computing device was last unlocked and/or an input data type that indicates whether a speaker's mobile computing device is in short-range communication with a particular device; obtaining, without requiring the speaker to provide explicit information, one or more data values that correspond to the identified one or more types of data for authenticating the selected voice action; and providing, to the selected service provider, an indication of the identity of the speaker determined using the audio data and the voiceprint for the speaker, the obtained one or more data values, and a request to perform the selected voice action.