Need help on Scheduled task for VM snapshot

I am trying to create a script to schedule run once snapshots.

I have looked at the samples but found this issue is more helpful:

https://github.com/vmware/pyvmomi/issues/452

Hence I have wrote my code:

scheduleTime = "29/03/2021 20:50"
dt = datetime.strptime(scheduleTime, '%d/%m/%Y %H:%M')
spec = vim.scheduler.ScheduledTaskSpec()
spec.name = 'jsmith'
spec.description = "VM Snapshot scheduled for jsmith"
spec.scheduler = vim.scheduler.OnceTaskScheduler()
spec.scheduler.runAt = dt
spec.action = vim.action.MethodAction()
spec.action.name = vim.VirtualMachine.CreateSnapshot
spec.action.argument = [vim.MethodActionArgument()] * 4
spec.action.argument[0].value = "spec.name"
spec.action.argument[1].value = "spec.description"
spec.action.argument[2].value = False
spec.action.argument[3].value = False
spec.enabled = True

si.content.scheduledTaskManager.CreateScheduledTask(vm, spec)

I keep getting this error:

    si.content.scheduledTaskManager.CreateScheduledTask(vm, spec)
  File "/home/adm-qhan/miniconda3/envs/pyvmomi/lib/python3.7/site-packages/pyVmomi/VmomiSupport.py", line 706, in <lambda>
    self.f(*(self.args + (obj,) + args), **kwargs)
  File "/home/adm-qhan/miniconda3/envs/pyvmomi/lib/python3.7/site-packages/pyVmomi/VmomiSupport.py", line 512, in _InvokeMethod
    return self._stub.InvokeMethod(self, info, args)
  File "/home/adm-qhan/miniconda3/envs/pyvmomi/lib/python3.7/site-packages/pyVmomi/SoapAdapter.py", line 1397, in InvokeMethod
    raise obj # pylint: disable-msg=E0702
pyVmomi.VmomiSupport.InvalidArgument: (vmodl.fault.InvalidArgument) {
   dynamicType = <unset>,
   dynamicProperty = (vmodl.DynamicProperty) [],
   msg = 'A specified parameter was not correct: ',
   faultCause = <unset>,
   faultMessage = (vmodl.LocalizableMessage) [],
   invalidProperty = <unset>
}

Which parameter it could be wrong in this case?

The reported failure occurs at si.content.scheduledTaskManager.CreateScheduledTask(vm, spec); start by comparing the ScheduledTaskSpec and MethodAction fields in the shown script with the referenced sample issue. Done means identifying the invalid parameter and documenting or reproducing a corrected scheduled VM snapshot request.