Try this:
function onKill(cid, target)
if(isPlayer(cid) == TRUE) then
if getPlayerLevel(cid) >= (getPlayerLevel(cid)/2) then
doSetItemSpecialDescription(doPlayerAddItem(cid,5943,1), "This is the heart of "..getPlayerName(target).."["..getPlayerLevel(target).."]. He or She was killed by...