Used to agree generally while implying that further discussion on details is needed. I support your plan in principle; let's hash out the specifics tomorrow.
Pro Tip 2/3
Lacks Detail
Indicates that an idea is sound, but specifics are either unresolved or not provided. The project seems good in principle, but what about the budget?
Pro Tip 3/3
Conditional Assent
Shows conditional acceptance and that more information could affect the final decision. We accept the deal in principle, pending a legal review.