ACL script to add desc and sthead to all the tables in the document automatically

Hi All I'm new in ACL, and I want to insert automatically desc and sthead in the tables at the document, I was thinking to do something like this:

function _addMissingTags(){

    oid = oid_first();

    oid_find_children(oid,$tables,"table");

  for( i = 1; i < count($tables); i++){

         oid_table = $table[i];

         goto_oid( oid_table);

          oid_find_children(oid,$desc,"desc");

           if(count($desc) <  1){

             insert("<desc></desc>");

           }

    }

}

but it is not working, any help?

Thanks!!