The Book of Occultation — al-Ṭūsī · Hadith 657 (#Ḥadīth #7)
Chapter 48 | Appointees of the four special deputies of the Imam
ومنهم أحمد بن إسحاق وجماعة خرج التوقيع في مدحهم:
And among them Ahmad bin Ishaq, Ibrahim bin Muhammad Hamadani and Ahmad bin Hamza bin Yasi:
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).