<?php
// no direct access
defined('_JEXEC') or die ;

// Load the K2 Plugin API
JLoader::register('K2Plugin', JPATH_ADMINISTRATOR.'/components/com_k2/lib/k2plugin.php');

// Initiate class to hold plugin events
class plgK2k2seo extends K2Plugin
{

        // Some params
        var $pluginName = 'k2seo';
        var $pluginNameHumanReadable = 'SEO Tags';

        function plgK2k2seo(&$subject, $params)
        {
                parent::__construct($subject, $params);
        }

        function onK2PrepareContent(&$item, &$params, $limitstart)
        {
                $tags=& JFactory::getDocument();
                $tags->setTitle('Hello');
                $tags->setDescription('Hello 2'); 
                //This is a test 
        }

} 

$tags=& JFactory::getDocument();
                $tags->setTitle('Hello');
                $tags->setDescription('Hello 2');