Validation: AroundInvoke signature

Object <METHOD>(InvocationContext) throws Exception

It MUST have the return value object. I can say from experience if this is not there you'll get some pretty strange null pointers from the JVM proxy.
It also MUST have 'throws Exception' if it doesn't the app will not be able to throw any checked exceptions – they will all count as system exceptions.
And of course it MUST have InvocationContext.