What is the effect of a rule that in effect relied on plea agreements drafted by prosecutors to give defendants the equivalent of Rule 11 warnings?

5 In this respect, we reaffirm what we indicated in Ferrara, namely, that serious problems would follow from a rule that in effect relied on plea agreements, drafted by prosecutors, to give defendants the equivalent of Rule 11 warnings. This is because there can be no guarantee that a defendant will read his plea agreement or have it explained in detail to him by his attorney. Rule 11, instead, by mandating that warnings be given in open court, seeks to assure that the warnings will be heard and understood by defendants. Cf. McCarthy v. United States, 394 U.S. 459, 467, 89 S.Ct. 1166, 22 L.Ed.2d 418 (1969) (stressing the importance in Rule 11 proceedings of direct interrogation of the defendant by the district court in order to facilitate the determination of the voluntariness of a defendant's guilty plea).