The ContextSwitch helper requires the "format" parameter to be set (see Zend_Controller_Action_Helper_ContextSwitch#initContext()).
However, you could cheat and add the format parameter to the request at the
top of your init() hook:
public function init()
{
$this->getRequest()->setParam('format', 'json');
/* ... the rest of your code ... */
}
--
*Hector Virgen*
Sr. Web Developer
http://www.virgentech.com
