The SmartAPI project aims to maximize the FAIRness (Findability, Accessibility, Interoperability, and Reusability) of web-based Application Programming Interfaces (APIs). Rich metadata is essential to properly describe your API so that it becomes discoverable, connected, and reusable. We have developed a openAPI-based specification for defining the key API metadata elements and value sets. SmartAPI's leverage the Open API specification v3 and JSON-LD for providing semantically annotated JSON content that can be treated as Linked Data.