So there was a problem where the slash animation doesn't work, The AnimationController Is Inside of the tool and the Animator Is stored In the AnimationController which the animator stores the SlashAnimation
script:
local Tool = script.Parent
local AnimationController = Tool.AnimationController
local Animator = AnimationController.Animator
local Animation = Animator.SlashAnim
local AnimationTrack
Tool.Activated:Connect(function()
AnimationTrack = AnimationController.Animator:LoadAnimation(Animation)
AnimationTrack:Play()
end)

3 comments
Question: Is that a local script or a server script?
I believe that AnimatonController needs to be a child of a Player's Character.
server script