OpenAPI Specification is a machine and human readable way to describe APIs, from endpoints to examples. From these descriptions we can generate documentation, create libraries, and ensure that our users know exactly what to expect from our APIs. This talk introduces you to the OpenAPI standard, showing how to describe APIs and looking at some popular API examples. Good tools are essential so we'll look at some of the open source tools available to working with OpenAPI easier. We'll cover the benefits of using an open standard to describe your APIs and discuss what you can do next, like publishing documentation, generating code, and teaching LLMs new tricks. Learn about what's coming up in the world of OpenAPI, and how to get involved with this open standard and its community.