Message type indicates what product this event will be used for. In this case, the message_type will be conversation
"conversation"
This is the type of event that is being sent back. This field will be present on all events and can be used to distinguish between different event types.
"conversation.utterance"
The unique identifier for the conversation.
"c123456"
This is a unique identifier for a given utterance. In this case, it will be the utterance the replica is speaking.
"83294d9f-8306-491b-a284-791f56c8383f"
This object will contain the speech
property which contains the contents of the utterance and will optionally contain the visual_context
property.