Who is Tzu-kung from The Analects and what is their importance?

Tzu-kung is a disciple of Confucius who is the only one of the three best known disciples to live longer than Confucius. He is the most distinguished of Confucius' early disciples. He has a successful career as a diplomat and merchant. Confucius says he lacks the qualities of a ruler since he is a specialist but is last mentioned holding office in Wei. His success making money makes him intolerant of unnecessary spending. Confucius compliments his intelligence but not his moral qualities. The Master thinks Tzu-kung is not capable of benevolence. Confucius thinks he is more likely to talk about wanting benevolence than actually practicing it. The disciple leaves many eloquent compliments about Confucius. Tzu-kung describes the Master as cordial, respectful, a sage, frugal and deferential.