Could someone help fix my tool local script?

There are a few errors in this script. First of all, you call onKeyDown with two arguments, the mouse argument being unnecessary since it is already globally defined as a variable, not to mention the actual function has space for only one parameter of input. You can actually abbreviate your listening event line (line 22) by saying mouse.KeyDown:connect(onKeyDown) which would directly attach your key parameter to the function when it is called.

Second, change your key == "E" to Key == "e" . Because you said Key = key:lower() you should use this to your advantage and utilize the variable, since it will always be lowercase based on your definition. At the moment you are using the regular key, the one that could be capital or lowercase.

Third, while I'm not sure of what your userdata looks like, Player = script.Parent.Parent seems a little far fetched to me. I'm not sure WHERE this localscript is, but if it's underneath a tool/hopperbin object, which would be inside the Backpack, the Player would be three parents up, not two. You may want to check this; I could be completely wrong if you set it up differently.

Forth, your ends are positioned awkwardly. function Lol(mouse) is only defined as a function when the function onKeyDown is called since the end for onKeyDown surround function Lol(mouse) . To fix this, simply move the end on line 24 to the spot right before line 21 (where your other function starts). You may want to tab your code appropriately (indenting based on the level/hierarchy of code) so you can notice these encompass errors quicker.

This is what I have when I combine all these fixes to your code. I also added an Unequipped event to make sure the key doesn't work after the tool is deselected, and properly tabbed the code. This should make it easier to read, and I highly recommend you follow this format in future coding.

local Enabled = true
local wand = script.Parent
local stick = wand.Handle
local Player = script.Parent.Parent
local mouse = Player:GetMouse()
local theconnector

function onKeyDown(key)
    if not Enabled then return end
    Enabled = false
    local Key = key:lower()
    if Key == "e" then
        local x = Instance.new("Part", game.Workspace)
    end
    Enabled = true
end

function Lol()
    theconnector = mouse.KeyDown:connect(onKeyDown)
end

function NotLol()
    theconnector:disconnect()
end

wand.Equipped:connect(Lol)
wand.Unequipped:connect(NotLol)

I hope this helped, and if it did, please make sure to upvote!