More api help please

More api help please

Can you please tell me what's wrong with the following ....

var options = 
      {
'method' : 'get',
        'invoice_number_contains' : '30999',
      }; 
  var response = UrlFetchApp.fetch(url,options);
  Logger.log(response);

All invoices are returned ?

The api help really could do with some working examples !