There is very little required by law to make a contract enforceable. Some types of contracts are required to be in writing, such as anything to do with land, contracts for goods worth $500 or more, and contracts for services that cannot be performed in a year.
Otherwise, valid contracts should include the names of the parties, be signed by both parties and have a method for determining the price. A contract should be specific enough that a third person could determine what the parties agreed to.
Beyond that, it is advisable to be as specific as possible so you don’t leave key provisions undiscussed or ambiguous. How much are you buying, is it by the unit, the case or the gross? Are you buying “chickens” or “pullets”? When are you paying? What happens if delivery is late? If payment is late?
