Considering that Toshiie once urged Masamune to come to the capital (Kyoto), and that he served as a soja (person in charge of informing a shogun or daimyo of the name of visitors to the residence before the meeting) to Hideyoshi, Toshiie seemed to be in charge of diplomacy with the date clan (the documents of the Date family).
先に上洛を促していることといい、秀吉への奏者を務めていることといい、利家は伊達氏との外交についても担当していた様子である（伊達家文書）。