REST APIs are everywhere but keeping them organized and consistent can be very difficult, especially as APIs grow and teams change. Do we write a bunch of code and then document it and hope we were accurate? Do we write a bunch of markdown documents describing the ideal API before coding starts and hope that we got it right? How do we communicate these changes over time to the people using our API?

Instead, let's explore how the OpenAPI specification (formerly called Swagger) can help us with an API-first approach. In this talk we'll learn what problems OpenAPI was designed to solve, how to use it to make your REST APIs more consistent, and how we can use it to make our development process a lot simpler. Once we know the basics, we'll use it to create our own API, validate that it is consistent, and generate not only server code but clients in multiple languages. At the end of this talk, you'll know what kind of problems OpenAPI solves, and how to use it to make your REST APIs sing!