Package: OpenAPI Generator
Reason for nomination:
OpenAPI is a very easy to create YAML file for recording and iterating API specs. While this is very important already, most power comes from the ecosystem around it - which the OpenAPI Generator for Swift is one.
The OpenAPI Generator generates Swift types for all OpenAPI types specified. In addition, it lays out protocol definitions for the server to implement - ensuring that any implementation in Swift is spec-compliant to the OpenAPI specification.
Finally, it also generates a client implementation, so you can download an existing OpenAPI spec and get up and running with the push of a button.
All this makes it very easy and reliable to connect to- or create an API.