You will work with a team of graphic designers, copywriters, creative directors, brainstorming and collaborating together to make ideas happen. You need to contribute as well and keep yourself updated on what's happening in the world to be able to bring something to the table. As an art director is expected to be confident on the direction your are giving to your work and make all the pieces work together as a whole and making sense with the brief.
Also, you need to be prepare to work extra, if you want to participate in the Cannes Lions Festival and be constantly thinking about it. A simple brief, no matter which one, could become a potential Cannes Lions Winner.