"Gukansho" (Jottings of a Fool), "Kojidan" (Talks of the Past) and "Zoku Kojidan" (Talks of the Past, continued) contained anecdotes about his talent for writing and the August 23, 1184 entry in FUJIWARA no Kanezane's diary "Gyokuyo" refers to Toshinori's prediction that 'war will not cease as long as the Retired Emperor Goshirakawa holds power' as a 'proverb of a wise man.'
『愚管抄』や『古事談』『続古事談』にその文才を物語る逸話があり、また『玉葉』元暦元年（1184年）7月9日条にも、かつて俊憲が「後白河院のもとでは戦乱が止まないであろう」と予言していたことが「聖人格言」として紹介されている。