Thats what I used at my previous startup and had a lot of luck with it. Our backend used NestJS which allowed us to define APIs and DTOs using decorators which automatically generated OpenAPI json files. Then our clients would load the json and generate their own SDK as a library. It worked extremely well. It worked so well that I don't really understand what problem Stainless is solving. We didn't ship public SDKs. So, maybe that's what I'm missing, but for our internal clients OpenAPI generators worked great. We generated SDKs on the fly for TypeScript (Node services and Angular clients), Dart (flutter), Kotlin (android), and Swift (iOS). For the most part it all "just worked" for our use case.