In your page http://www.telerik.com/help/aspnet-ajax/autocompletebox-onclientrequestfailed.html you only have one message to show to the user, why not return de http status code?

In this moment the workaround suggested by your team is:
<script>
    Telerik.Web.UI.WebServiceLoader.prototype._onWebServiceError = function (error, context)
    {
        var errorEventArgs = new Telerik.Web.UI.WebServiceLoaderErrorEventArgs(error.get_statusCode().toString(), context);
        this._raiseEvent("loadingError", errorEventArgs);
    }
 
    function OnClientRequestFailed(sender, args) {
        console.log(args.get_errorMessage());
    }
</script>