Sending string parameter to action = track leanplum Rest Api not working

I want to send string parameters to Leanplum api using a script action For example param: {"Element": "Hi"}

var request:URLRequest = new URLRequest("https://www.leanplum.com/api");
request.method = URLRequestMethod.GET;

var variables:URLVariables = urlVariables;
variables.userId = userId;      
variables.event = eventName;
var params:Object = new Object();
params.Element = "Hi";
var paramStr:String = JSON.stringify(params);
variables.params = paramStr;
variables.appId = appId;
variables.clientKey = clientKeyProduction;
variables.apiVersion = apiVersion;
variables.action = "track";
variables.versionName = AppInfo.getInstance().appVersion;
request.data = variables;
var loader:URLLoader = new URLLoader();

loader.addEventListener(Event.COMPLETE, function(e:Event):void {
                trace(e.target.data);
            });

loader.addEventListener(IOErrorEvent.IO_ERROR, function(e:IOErrorEvent):void {
                trace(e.target.data);
            });

loader.load(request);

      

        
        
        
      

    

This is the actual request (Application ID and ClientKey are bogus): https://www.leanplum.com/api?clientKey=V42fKaJaBuE&userId=1010¶ms= {"Item": "Ur"} & app = id; apiVersion = 1.0.6 & Info = Lou

Coded request: https: //www.leanplum.com%2Fapi%3FclientKey%3DV42fKaJaBuE%26userId%3D1010%26params%3D%7B%22Element%22%3A%22Ur%22% 7D% 26appId% 3DHEVLDlXiaction% 26appId% 3DHEVLDlXiaction% % 3Dtrack% 26versionName% 3D2.3.0% 26apiVersion% 3D1.0.6% 26info% 3DLu

if i execute the request above in any rest client i get the same success status: true.

I get a response {"response": [{"success": true}]}, but I can't find the parameters with a value string in the Leanplum toolbar, its the list parameter name but not the String Value parameter for the parameter.