I have a problem playing an animation in a tool, it gave me an error why?

See the edited answer below the original answer

So you can’t simply play the animation just like that. You have to actually load it and then play the loaded animation.

Here’s what your script should look like :

local tool = script.Parent
local handle = tool:WaitForChild("Handle")
local animation = script.Parent.EquippedAnimation
local loadedanim

tool.Equipped:Connect(function()
    local humanoid = script.Parent.Parent:FindFirstChild('Humanoid') --Finds humanoid
    if humanoid then
        loadedanim = humanoid:LoadAnimation(animation) --Loads animation
    end
end)

tool.Activated:Connect(function()
    loadedanim:Play() -- Plays loaded animation
end)

tool.Unequipped:Connect(function()
    --Other code
end)

So what this does is it tries to find a humanoid in whatever character equips it. If it finds one, it’ll load the animation and return something called an AnimationTrack, which is where you get to use the :Play() function. It gets saved as a variable and when the tool is activated, the animation will play.

If you have any questions, just comment!

Answer Edit

Okay, so I checked your new script and well, the way you edited it pretty much broke the whole thing. Here's the fixed version :

local tool = script.Parent
local handle = tool:WaitForChild("Handle")
local animation = script.Parent.EquippedAnimation
local animation2 = script.Parent.R15Animation
local loadedanim

tool.Equipped:Connect(function()
    local humanoid = script.Parent.Parent:FindFirstChild('Humanoid') --LocalPlayer will not work in server scripts. Also add more parents if this script is not directly parented to the tool.
    if humanoid then
        if humanoid.RigType == Enum.HumanoidRigType.R15 then --Use enums instead of strings
            loadedanim = humanoid:LoadAnimation(animation2) --Putting "local" before the variable seperates it from the actual variable. Don't use local in this part.
        else
            loadedanim = humanoid:LoadAnimation(animation) --Don't use local in this one too.
        end
    end
end)

tool.Activated:Connect(function()
    loadedanim:Play()
end)

tool.Unequipped:Connect(function()
    --Other code
end)

If you have any more questions, just comment. Be careful when editing this too.