The APIs.json URL for an API contract provides the source of where a contract originated. This URL helps consumers of a contract access the latest copy of an API contract, and can also help establish the authoritative nature of an API contract–meaning the API contract is created and maintained by an API producer.
The URLs used across the properties for an API contract can be compared with the contract URL to help establish the provenance and ownership of a contract. The URL of a contract is often in the root of an API portal as well as in the root of a GitHub repository that public or private. The URL for an API contract will matter in many different ways to both producer and consumer of the contract.
While some API contracts will cover what is happening within an API portal, it is much quicker and easier to create and maintain API contracts via Git repositories, which can be validated as producer oriented or consumer oriented in other ways. API contracts can be made centralized or federated, with the APIs.json URL playing a key role in discovery no matter which approach is taken.