Note: Please place your code in functions.php of your current theme.

Hook after successfully adding new shipment through API

  function custom_wpcargo_api_after_add_shipment_calback($shipmentID, $request){
    // Do your stuff here..
  }
  add_action('wpcargo_api_after_add_shipment', 'custom_wpcargo_api_after_add_shipment_calback', 10 ,2);
  

Hook after successfully updating of shipment through API

  function custom_wpcargo_api_after_update_shipment_calback($shipmentID, $request){
    // Do your stuff here..
  }
  add_action('wpcargo_api_after_update_shipment', 'custom_wpcargo_api_after_update_shipment_calback', 10 ,2);