Typos on line 47: "descriptioin" -> "description"

That you for this module! I'm going to use the hook_nodewords() you've defined to build meta data based on path.

That said, I've uncovered a small bug:

      if ( $type == 'node' && (!isset($tags['descriptioin']) || empty($tags['descriptioin'])) && count($ids) == 1) {

Should read:

      if ( $type == 'node' && (!isset($tags['description']) || empty($tags['description'])) && count($ids) == 1) {