This disclosure describes techniques in which one or more computing devices receive a signal from a first client computing device. The signal indicates that the first client computing device is available for participation in a communication session that enables communication between the first client computing device and one or more other client computing devices. The one or more computing devices determine a context for a topic of discussion associated with the communication session. The context is associated with a content item capable of being outputted by the first client computing device. Responsive to receiving the signal, the one or more computing devices initiate the communication session and send an invitation to at least one of the one or more other client computing devices to join the communication session. The invitation indicates the context of the communication session to at least one of the one or more other client computing devices.