in reply to Do you accept the terms of our agreement?
Authorised access to an interface is just that.
If your organisation has permission from the other organisation to use the XML interface (which neither enforces a disclaimer nor proffers one) then you've fulfilled your obligations as a developer (unless your organisation is located in a country with extremely strong privacy laws - I believe Germany and France are examples - where you may be requred to make sure that your code is compliant with privacy statutes).
If your management feels that the disclaimer (from the non-XML interface) contains information that would be truly important (legally) to your users (and that isn't covered by in-house handbooks or guides), you might have your legal department draft a disclaimer for your own organisation which can be displayed by your application.
Displaying the other organisation's disclaimer does nothing to cover you nor your organisation.