How to check if player has tool?

So I'm trying to make a class-based game. Right now I'm testing it out on roblox gear.

So. I'm trying to prevent the person from being able to click again if they already have the tool. Here's the script:

textButton = script.Parent
spawns = {game.Workspace.SpawnLocation1 , game.Workspace.SpawnLocation2 , game.Workspace.SpawnLocation3 , game.Workspace.SpawnLocation4}
player = script.Parent.Parent.Parent.Parent
Trowel = game.ReplicatedStorage.ClassicTrowel:Clone() 
already = player.Backpack:FindFirstChild("ClassicTrowel")

if already == nil then
textButton.MouseButton1Down:connect(function()
    script.Parent.Text = "5"
    wait(1)
    script.Parent.Text = "4"
    wait(1)
    script.Parent.Text = "3"
    wait(1)
    script.Parent.Text = "2"
    wait(1)
    script.Parent.Text = "1"
    wait(1)
    player.Character:MoveTo(spawns[math.random(1, #spawns)].Position)
    player.Character.Humanoid.MaxHealth = 200
    player.Character.Humanoid.Health = 200
    Trowel:Clone().Parent = player.Backpack 
    Trowel:Clone().Parent = player.StarterGear
    script.Parent.Text = "Change to Builder"
end)
else return
    end