Right, so I'm trying to essentially query all the objects (e.g. all opportunities).
Documentation says this:
Retrieves one or more MObjects using a combination of criteria consisting of:
Zero or one unique ID, either the Marketo ID or external ID
Zero or more attribute filters as name/value/comparison trios
Zero or more associated object filters as object name/ID pairs
Which I take to mean that all the parmaeters EXCEPT for Type are optional. Is this not the case? I've also tried specifying a single attribute filter, but I still get parameter required message.