Speakeasy

Speakeasy generates production-ready developer tooling from OpenAPI documents: type-safe SDKs in 12 languages (Python, TypeScript, Go, Java, C#, PHP, Ruby, and more), Terraform providers, MCP servers, Postman collections, and CLIs. In September 2026 the company partnered with Google to open-source its Go-based generator under AGPL-3.0 after Google's previous proprietary SDK vendor abruptly shut down — Google now uses it for its Gemini Interactions, Agents, and Webhooks APIs, and reports the pipeline needs roughly one engineer to maintain versus several for handcrafted generators.

The honest caveat: the open-source generator is AGPL-3.0 licensed, which is a non-starter for some companies without a commercial license from Speakeasy. Output quality depends heavily on the quality of your OpenAPI spec — garbage in, garbage out. The hosted platform's advanced governance features (the 'AI control plane' for agent access) are enterprise-tier, and smaller API teams may find Fern's simpler open-core model easier to adopt.

Install the CLI or use the hosted platform at speakeasy.com. Point it at your OpenAPI 3.0/3.1 document and select target languages; the open-source generator is at github.com/speakeasy-api/openapi-generation.