How to prevent a duplicated tool in a player's inventory?

So, im making a game where you find objects (gears/tools). I made a ClickGiver (a part) for the tool, but i want the player to have no more than 1 copy of the same tool. Is there a way to put a function for do it in the same script or i need to insert a LocalScript?

Here is how the giver works:

function GearGive(x)
	local y = x.Backpack
	local z = game.Lighting["ClassicSword"] --Change "GEARNAME" to the name of the item.
	z:Clone().Parent = y   -- put item in lightning.
end

script.Parent.ClickDetector.MouseClick:connect(GearGive)