What was the irony of Nick's attendance at the party?

Answer 1

Tom attended Gatsby's party purposely to keep Daisy closer from Gatsby's real intension of the party whom he knows is because of Daisy.

Answer 2

The irony of Nick attending Gatsby's party is that despite his initial reluctance and skepticism, he ends up getting drawn into and becoming part of the extravagant and superficial world that he was originally critical of. This highlights the allure and seductive nature of the lifestyle that Gatsby represents, despite Nick's initial reservations.