We've been talking about the concept of an API Economy for a while now. Over the past few years we've seen most software products move away from individual installations, into the Cloud, providing a "software-as-a-service" model for the consumption of their features. When one starts refering to software as a service, APIs become indispensible.
The OpenAPI Specification (formally known as Swagger) describes APIs in a way that is standardized, machine-readable, and programming language-agnostic. It is an open source project hosted by the Linux Foundation.
There have been many announcements regarding frameworks or tools supporting this standard: For example, Eclipse MicroProfile 1.3 provides a set of annotations that can be used on top of JAX-RS, and version 3.5.2 of Eclipse Vert.x provides automatic requests validation.