His involvement at that time in compiling Nihon Koki is proof of his high capability, since a noble could not become involved in compiling a history book unless the noble was a capable official.
この時期には日本後紀の編纂作業にも従事しているが、能吏でなければ史書編纂に携わることはあり得ず、このことも古嗣の有能ぶりを示している。