What Service Operation validates a chartfield combination? Or returns the list of valid chartfields?

We're trying to integrate an external cashiering application with PeopleSoft Financials. We're trying to determine which Service Operations validate or share chartfield combinations.

1) Which validates a chartfield combination?

COMBO_CF_EDIT_REQUEST does some validation, but it only seems to validate the business unit and ledger group. Any combination of chartfields beyond that come back as "valid" whether they're valid or not. Is there a better Service Operation to validate whatever chartfield combinations are passed in?

2) Which returns a complete list of valid chartfield combinations? We need to share the entire list of valid chartfield combinations with an external application. What web service is supposed to do this?