gapi.client.request({ 'path': 'https://api.appspot.com/_ah/api/', 'method': 'POST', 'params': { 'key': 'value' }, 'headers': { 'customheader': 'test', 'Authorization': 'Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==' }}).execute(function(resp) { console.log(resp);});