curl --request POST \
  --url https://api.cartesia.ai/agents/calls \
  --header 'Authorization: Bearer <token>' \
  --header 'Cartesia-Version: <cartesia-version>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "from_number_id": "<string>",
  "agent_id": "<string>",
  "outbound_calls": [
    {
      "to_number": "<string>",
      "metadata": {}
    }
  ],
  "ringing_timeout_seconds": 42,
  "max_call_duration_minutes": 123
}
'

{
  "calls": [
    {
      "number": "<string>",
      "agent_call_id": "<string>",
      "error": {}
    }
  ]
}