curl --request POST \
  --url https://api.getoutbox.ai/agent/call/{agent_id} \
  --header 'Authorization: <api-key>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "phone_number": "<string>",
  "full_name": "<string>",
  "agent_number": "<string>",
  "external_customer_id": "<string>",
  "context": {},
  "first_message": "<string>",
  "scheduled_at": "2023-11-07T05:31:56Z"
}
'

{
  "id": "<string>",
  "status": "<string>"
}