What defines an accessory contract in legal terms?

An accessory contract is characterized by its purpose of securing the performance of an underlying obligation. This type of contract exists to provide additional security or guarantees related to a primary contract. For example, a common form of an accessory contract is a suretyship, where one party agrees to be responsible for the performance or obligations of another party if they fail to execute their duties. The key aspect of accessory contracts is that they are dependent on a principal obligation; they do not stand alone but rather support or enhance the enforceability of the primary agreement.

The other options do not accurately reflect the nature of accessory contracts. A foundational agreement suggests an independent contract that does not hinge on another obligation, while establishing an agency relationship relates more to representation than securing an obligation. Documenting a unilateral act refers to a transaction where only one party makes a promise, which does not align with the reciprocal nature of accessory contracts designed to ensure obligations are met.