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.
Stoplight
Design-first platform for creating, governing, and documenting OpenAPI specifications. Bundles a visual editor, Spectral (JSON/YAML linter), Prism (mock server), and Elements (docs renderer) into one workflow. Teams use it to enforce API style guides across large API portfolios.