This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Shaykh al-Tusi compiled two further collections of Prophetic and Imami hadith, Tahdhib al-Ahkam and al-Istibsar, a documented pair of works distinct from a single compilation undertaken once and left as his only contribution to the field. Together with al-Kulayni's earlier Al-Kafi and a fourth compilation, these two works make up the Four Books forming the core of the Twelver hadith canon, a documented shared standing distinct from a text that circulated only within al-Tusi's own immediate circle of students.
Later tradition also credits al-Tusi with founding the systematic, independent study of Shi'a legal method, usul al-fiqh, as a discipline in its own right, a documented methodological legacy distinct from the hadith compilation that occupies two of the Four Books. That the same scholar is credited both with contributing two of Twelver Islam's four foundational hadith collections and with establishing legal method as its own field of study is recorded as a doubled contribution, compiler and methodologist together, rather than a single specialized achievement.
That one jurist's work produced both two of the four texts later generations turned to first for transmitted hadith and the very discipline of legal method those generations then used to reason from them marks Shaykh al-Tusi's combined legacy as a documented case where a single scholar supplied Twelver jurisprudence with both its raw source material and the systematic method for working through it.