add: menuItem.setAttribute('tooltiptext', item.fields.getProperty('description')); 
context:         function(feed, e) {            if(!feed) throw e;            var menus = {};            function menuFor(category) {                if(!menus[category]) {                    var menu = document.createElement('menu');                    menu.setAttribute('label', category);                    menuPopup.insertBefore(menu, menuPopup.getElementsByTagName('menuseparator')[0]);                    var popup = document.createElement('menupopup');                    menu.appendChild(popup);                    menus[category] = popup;                }                return menus[category];            }            for(var i=0; i<feed.items.length; i++) {                var item = feed.items.queryElementAt(i, Ci.nsIFeedEntry);                var menuItem = document.createElement('menuitem');                menuItem.setAttribute('label', item.fields.getProperty('title'));                menuItem.setAttribute('value', item.fields.getProperty('link'));                menuFor(item.fields.getProperty('dc:subject')).appendChild(menuItem);            }        });
meta: 1705	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/1705/e7d04a75eccffbfae19b816bcabf8e86a510a119/sameplace.js/buggy/chrome/content/sameplace.js