DOUGLAS GINSBURG, Federal Judge, U.S. Court of Appeals, D.C. Circuit:
The president’s cabinet, including the vice president and the heads of the executive departments, together advise the president.
The Constitution doesn't even mention a cabinet. Or the agency whose heads became the cabinet. Article II simply provides that the president may, with the approval of the senate, appoint the heads in the departments and require their opinions in writing.
The first executive departments created by the Congress were the Department of State, the Treasury, the Department of War, later Defense. And the post of attorney general, leading to what became the Department of Justice.
Owing to the importance of their roles, the leaders of those departments remain the key members of the cabinet – sometimes referred to as the inner cabinet.

Nothing compelled President Washington to form a cabinet, but he knew firsthand the value of good advice. As commander of the Continental Army during the American Revolution, Washington held councils of war with his generals.
The vice president didn’t become a member of the cabinet until 1921 during the administration of President Warren Harding.

Vice President Calvin Coolidge not only attended cabinet meetings but led them when the president was away.
Strong cabinet members can champion the president’s policies as well as lead their departments. But

a cabinet appointment can also backfire. Take President Harding: his Secretary of the Interior was convicted of bribery in a scandal so notorious, it may have driven the president to an early grave.