curl --request POST \
  --url https://your-instance.example.com/api/webhook/elevenlabs/tools/transfer \
  --header 'Content-Type: application/json' \
  --data '
{
  "reason": "Caller asked for a human supervisor",
  "conversation_id": "conv_8f3d1b9c2e7a4f0b9a4d2c1e6e2f8c01",
  "called_id": "+12362320246"
}
'

{
  "success": false,
  "message": "Transfer is not yet implemented — please ask the caller to hold while a human agent joins."
}