Internal call ID assigned by CallManager.
E.164 phone number to call from.
E.164 phone number to call.
Call interaction mode.
Optional messagePre-composed message (for 'notify' mode).
Optional notifyTTS voice to use for notify-mode messages.
Webhook URL the provider should call back to.
Optional statusStatus callback URL for call state changes.
Optional mediaMedia stream WebSocket URL (for 'conversation' mode).
Optional mediaAuth token appended to media stream URL for validation.
Parameters for initiating an outbound call.