What's a VP to do?

No matter where you stand on the personalities currently nominated for Vice President of the United States, you may, like me, still be wondering what the official VP job description actually involves. I don't remember that being stressed on my 8th grade Constitution test. According to this Washington Post article there is some historical precedence for this lack of clarity - the "founding fathers" didn't really know what a VP does in office either. John Adams called the VP role "the most insignificant office that ever the invention of man contrived or his imagination conceived." Walter Mondale (VP under Jimmy Carter) is credited with being the first VP to try to take on a more politically influential/meanginful role.