Is there a way to stop/reduce the damage that you're taking when you're using a tool?

So I'm asking that If I use a tool, can I stop taking damage?

Yes, there is a way.

Put extra script in the weapons you're using so, if you protect yourself with the tool, said weapons won't damage. Here's an example with the (new) Roblox sword:

--In Sword ModuleScript, replacing the end of Function "Sword:Connect()"
if player.Character.Protected then --You can check if an instance (ex. BoolValue) exists, or always have it on the player and check if it is true, for (literal) damage control
	GLib.TagHumanoid(humanoid, myPlayer, 1)
	humanoid:TakeDamage(doDamage)
end

Hope i helped! You know what to do from here, i assume.

There is a way to remove the damage taking. If it's like onTouched event, then there sure is.

local user = nil

script.Parent.Equipped:connect(function()
user = script.Parent.Parent
	script.Parent.Handle.Touched:connect(function(hit)
		if hit.Parent ~= user then
			local humanoid = hit.Parent:FindFirstChild("Humanoid")
			if humanoid then
				humanoid:TakeDamage(25)
			end
		end
	end)
end)

That avoids you getting damage, 'cause it detects if it's the user who's being hit, and if it's not, it'd move forward in the script.