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 mediaHost-issued stream credential; carrier-specific XML determines its transport, including Twilio custom parameters.
Parameters for initiating an outbound call.