Gnostic is a tool for building better REST APIs through knowledge. Gnostic reads declarative descriptions of REST APIs that conform to the OpenAPI Specification, reports errors, resolves internal dependencies, and puts the results in a binary form that can be used in any language that is supported by the Protocol Buffer tools. Gnostic models are validated and typed. This allows API tool developers to focus on their product and not worry about input validation and type checking. Gnostic calls plugins that implement a variety of API implementation and support features including generation of client and server support code.