Full Idea
KF is useful for explicating Peano arithmetic, but it certainly does not come to close to being a theory that contains its own truth predicate.
Gist of Idea
The KF theory is useful, but it is not a theory containing its own truth predicate
Source
Volker Halbach (Axiomatic Theories of Truth [2011], 16)
Book Reference
Halbach,Volker: 'Axiomatic Theories of Truth' [CUP 2011], p.229
A Reaction
Since it is a type-free theory, its main philosophical aspiration was to contain its own truth predicate, so that is bad news (for philosophers).