Assuming you're trying to invoke() on a timer, have you consulted the javadoc to see what the arg list for TimerMBean.addNotification is supposed to be?
Your arguments appear wrong (missing a String).
I believe it's String, String, Object, Date [long [,long]]
As for explaining "all operations" one can invoke on and MBeanServer I would recommend that the best place to look is the specificatin and javadocs.
Additionally, Juha's book is very clear and comes highly recommended.