This determines whether metadata is sent in requests to the custom provider. - off will not send any metadata. payload will look like { messages } - variable will send assistant.metadata as a variable on the payload. payload will look like { messages, metadata } - destructured will send assistant.metadata fields directly on the payload. payload will look like { messages, ...metadata } Further, variable and destructured will send call, phoneNumber, and customer objects in the payload. Default is variable.