onMissingTransaltion Error 400

[nordkite]

I added

public function actionMissingTranslation($category, $message, $language) {
    Yii::t($category, $message, null, null, $language);
}

in controllers/SiteController.php
and my config is

'jsTrans'=>array( 
        'class'=>'ext.JsTrans.JsTrans', 
        'categories'=>array('app'), // the categories to be made available 
        'languages'=>array('fr','es'), // the languages to be made available
        'onMissingTranslation'=>array('site/missingTranslation'), // optional route to handle untranslated messages
    ), 

When I acces site/missingTranslation it gives Error 400: Your request is invalid.
Can you tell how the url should look like?