how to set up azure mobile service to deliver periodic updates to a windows 8 (store) App?

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Mobile

Azure

WinRT

I want to add periodic tile updates to my windows store App, everything works ok if I provide a xml to the tileUpdateManager like for example this address http://wowzappelsalvador.azurewebsites.net/tiletest.xml[^].
The app works with an azure mobile service and the idea is to have the App tile updated using the same service so I created a read script on azure like this:

function read(query, user, request) {

    mssql.query("select imagenTile, nombreTip from verdetips.tipDiaLiveTileView", {
        success: function(results) {

            var xmlEscape = function (text) {
            return text.replace(/&/g, '&')
               .replace(/</g, '&lt;')
               .replace(/>/g, '&gt;')
               .replace(/"/g, '&quot;');
            }

             var payload = "<?xml version='1.0' encoding='UTF-8'?>" +
             "<tile><visual><binding template='TileWideImageAndText01'>" +
              "<image id='1' src='" + xmlEscape(results[0].imagenTile) + "' alt='Verde Tips'/>" +
              "<text id='1'>" + xmlEscape(results[0].nombreTip) + "</text>" +
              "</binding>" +
              "<binding template='TileSquareText04'>" +
              "<text id='1'>" + xmlEscape(results[0].nombreTip) + "</text>" +
              "</binding></visual></tile>";

             console.log(payload);
             request.respond(statusCodes.OK, payload);
        }
     });
}

when I call the table associated with this script I get the same text as on the .xml file but on a .json file and the tile update doesn't work, what am I missing?

Note: I've seen some sites explaining how to use push.wns.send on azure mobile services to send push or toast notifications but my case is a polled notification, client code as follows:

var notifications = Windows.UI.Notifications;
        var polledUri = new Windows.Foundation.Uri("http://verdetips.azure-mobile.net/tables/tipDiaLiveTile");
        //var polledUri = new Windows.Foundation.Uri("http://wowzappelsalvador.azurewebsites.net/tiletest.xml");
        var recurrence = notifications.PeriodicUpdateRecurrence.daily;
        var tileUpdater = notifications.TileUpdateManager.createTileUpdaterForApplication();
        tileUpdater.startPeriodicUpdate(polledUri, recurrence);

Any help would be much appreciated!