The document discusses Schema and Clojure.spec, two libraries for data validation and specification in Clojure. It provides an overview of Schema's capabilities for runtime validation, documentation, and data transformations. It also summarizes Clojure.spec's focus on specification through generative testing. The document compares the two approaches and argues that Schema is currently better for runtime validation in web applications, while Clojure.spec will be important for system-level specification.