How to add META DESCRIPTION tag to my pages

1. Proceed to Visual Editor, switch to HTML mode andu can insert a new template variable like this:
   
   <meta name='description' content='{$meta}'>
   
2. Then in BeforeDisplay event populate this variable:
   
   $xt->assign('meta', 'My meta info');
   

it is possible to obtain a specific name of a value associated with the current page using the variable $ xt
$xt->assign('meta', 'My meta info');
= $xt->assign('meta', '$value');