foo.clj

user> (reduce (fn [acc [keyseq type]]
                (update-in acc keyseq (fnil conj #{}) type))
              {}
              (for [[method objs] inputs
                    obj objs
                    [half fields] obj
                    [field value] fields]
                [[method half field] (type value)]))
{"SignIn" {:request {"InvitationID" #{nil}, "ReturnExpiredAuthenticationMethods" #{java.lang.Boolean}, "AuthInfo" #{nil clojure.lang.PersistentArrayMap}, "Version" #{nil}, "ApiVersion" #{java.lang.String}, "ClientInfo" #{clojure.lang.PersistentArrayMap}}, :response {"AuthenticationLevel" #{java.lang.Long}, "ExpiredAuthenticationMethods" #{nil clojure.lang.PersistentVector}, "ExpirationReason" #{nil}, "User" #{clojure.lang.PersistentArrayMap}, "Alerts" #{nil}, "NewSession" #{nil}, "ApiVersion" #{nil}}}}