Not everyone can jump right into a Kotlin Multiplatform world. Many developers have legacy codebases and need to support their businesses first. Yet, those developers can already use Kotlin to connect their platforms and realize significant value. In this talk, Patrick Cousins will teach you to build a DSL that defines a contract between an API and its clients. He will also make your DSL into a common vocabulary that translates platform idiosyncrasies. Then, by connecting it to CI, he'll enforce the contract to keep platforms on speaking terms. The examples in this talk will be from Sprout, an internal library in development at Etsy. The Sprout Kotlin DSL is the seed that generates code for many platforms: Retrofit endpoints, Moshi models, Swift, PHP, and more.