Fern
Takes an OpenAPI spec and generates hand-crafted-quality SDKs across TypeScript, Python, Go, Java, Ruby, C#, and PHP, plus integrated documentation sites. SDKs and docs stay in sync from a single source of truth. Used by Cohere, ElevenLabs, and Merge.
OpenAPI Generator
The most widely adopted open-source code generator forked from Swagger Codegen. Given an OpenAPI spec, generates API client SDKs, server stubs, and documentation for 50+ languages and frameworks. 26k+ GitHub stars, 600k weekly NPM downloads, and 30M Docker pulls.