These days, I spend a lot of time working with, designing, and implementing APIs. Since Meta is a microservices based application, the contracts that those APIs provide are crucial to designing the interactions with them. Quickly, maintaining good documentation and client libraries becomes nearly as important of a part of the applications as the code itself. Each step forward in functionality must provide solid footing to keep on building. A spectacular tool that we have been using is Apiary, a service that provides API documentation through a super set of markdown that is fully parsable, providing mocked APIs and examples through a single set of documentation.