Which Shia narrators can be considered reliable and trustworthy in our collection of Hadiths such as Al-Kafi? Is there a book or source that provides a list of narrators classified as reliable or unreliable?
The most authentic books of Hadeeth are our four books ; Al-Kaafi, Al-Tahtheeb, Al-istibsaar and Manila Yahdharuhul Faqeeh. Yet we don't claim that every narration in these books is hundred percent authentic as every expert in Hadeeth has the freedom of research and freedom of opinion in the authenticity. We are not like some Muslims who claim that every narration in Bukhari is authentic, despite the fact that many narrations in Bukhari book is clearly against Quran and against the dignity of the Prophet Muhammad (SAWA) e.g. false claims that he attempted suicide many times, he used to urinate while standing on the road and land of others, and many other false claims. (Look at A Journey in the two Saheeh by Sadiq Najmi).
Our scholars of Hadeeth have the research procedure continuous , not like others who closed the research on the Hadeeth and kept following blindly previous scholars.
if you want to know the authenticity of any Hadeeth,b you need to refer to the specialized scholar of your time. In general, the book called Al-Kaafi has the maximum number of authentic Hadeeths and it has more authentic narrations than the all six books of Hadeeth with our Sunni brothers.
Wassalam.