Both major league baseball contracts and minor league baseball contracts are signed by players who are offered spots on baseball teams. There are two separate leagues in Major League Baseball: the National League and the American League. The Major League Baseball Constitution controls Major League Baseball, also referred to as MLB. The Commissioner of Baseball directs the hiring of umpires and other MLB crews and also negotiates television contracts for Major league baseball. Baseball players who sign both major league baseball contracts and minor league baseball contracts often hire an agent to help negotiate the terms of their contract agreement, such as signing bonuses and other perks. Signing bonuses are common in league baseball contracts. Signing bonuses are upfront payments made to players when they sign a contract. Signing bonuses, especially in major league baseball contracts, are often quite large, and can be over a million dollars for particularly good players.