Stainless

Stainless is the SDK generation platform behind the official client libraries of major API companies including OpenAI, Anthropic, and Cloudflare — a strong signal of production-quality output. For teams maintaining API products that want SDK quality matching what developers experience from best-in-class API companies, Stainless's generation quality is the key differentiator. The enterprise track record reduces evaluation risk for teams with high SDK quality requirements.

Authentication uses API keys for the Stainless managed service. Access is currently invitation-based for new accounts, which should be factored into evaluation timelines for teams considering Stainless for new API products. The CLI and CI integrations handle the generation workflow similarly to Speakeasy.

Stainless generates SDKs from OpenAPI specifications with a focus on idiomatic, production-quality code in each target language. The generated code handles pagination, retries, streaming, and type safety in the way developers expect from each language's ecosystem rather than as language-agnostic wrappers. For agents maintaining API infrastructure, Stainless integration enables automated SDK publishing as part of the API release workflow.

Reliability is appropriate for a developer tooling service. SDK generation is triggered by spec changes rather than requiring continuous availability. The enterprise customer base implies production-grade reliability commitments appropriate for teams that depend on Stainless for their SDK release pipelines.

Documentation covers the configuration and CLI workflow clearly. Teams evaluating Stainless versus Speakeasy should assess the generated SDK quality for their specific target languages and API patterns — both platforms generate high-quality SDKs, and the choice often comes down to language coverage, specific API pattern handling, and team familiarity with the tooling.