How can you detect when there is a tool in your backpack?

I dont know how to know if a player has a tool in their inventory, can someone help me?

player.Backpack will let you know of all the tools that are NOT equipped. Otherwise, if equipped, the tool will be inside the character in the workplace.

a simple loop through their backpack/character will help you find a tool

You can simply insert a Local Script (StarterGui, ReplicatedFirst etc.) and you can get the player by:

local player = game.Players.LocalPlayer

Then you need to get the player's backpack:

local backpack = player:WaitForChild("Backpack")

Now, to check the items you have to loop through the player's backpack. First, you need to get the contents of the backpack.

local Contents = backpack:GetChildren()

Now you can simply loop through the contents:

for i, v in pairs(Contents) do
	if v:IsA("Tool") then -- this will check if there's a tool
		print(v)
	else
		print("No Tool") -- Prints No Tool when there is no tool
	end
end

Now, this will remove any type of possible errors related to backpack:

if Contents ~= nil then -- It will check whether player backpack's is empty or not
	-- Loop Code
end

Now, this is how your LocalScript must look:

--Variables--
local player = game.Players.LocalPlayer
local backpack = player:WaitForChild("Backpack")
local Contents = backpack:GetChildren()

--Main Code--
while wait(3) do -- It will loop the code every 3 sec
	if Contents ~= nil then
		for i, v in pairs(Contents) do
			if v:IsA("Tool") then 
				print(v)
			else
				print("No Tool") 
			end
		end
	end
end

Lemme know if it helps!