Stainless
The AI compiler that turns your OpenAPI spec into hand-crafted, production-ready SDKs across every major language.
Overview
Stainless is a developer platform that acts as an AI-powered compiler: feed it an OpenAPI specification and it generates idiomatic, production-grade client SDKs in TypeScript, Python, Go, Java, Kotlin, Ruby, PHP, C#, and Terraform — complete with auto-pagination, retry logic, streaming, rich typing, changelogs, documentation sites, MCP servers, and CLIs. Founded in New York in 2022 by Alex Rattray (ex-Stripe, CEO) and Mark McGranaghan (President/CTO), the company powered the official SDKs for OpenAI, Anthropic, Meta, Google, Cloudflare, Runway, and Groq before being acquired by Anthropic in May 2026 for over $300 million.
As of May 18, 2026, Anthropic acquired Stainless and wound down all hosted products. New signups and SDK generation are no longer available on the platform; existing customers retain full ownership of the SDKs they already generated and can continue modifying them. The Stainless team is now embedded in Anthropic's Claude Platform group, focused on making Claude agents more broadly connectable to APIs and third-party services. Developers seeking a replacement should evaluate Speakeasy, Fern, or the community open-source project Stainful (github.com/stainlu/stainful).
Pricing
Pricing shown for reference only. These figures reflect RECATOOLS research as of 16 Jun 2026 and may be out of date or incomplete. This is not financial or purchasing advice — always confirm the current price on the provider’s official website before making any decision.
Use cases
What you can produce with Stainless
- Production-ready, idiomatic SDKs in up to 9 languages from one OpenAPI spec
- Automated package publishing to npm, PyPI, Maven, RubyGems, and other registries
- Auto-generated documentation site with custom domain and AI chat support
- CLI tool and MCP server generation alongside client libraries
- Changelog generation and GitHub PR workflow for every API spec change
- Unit test scaffolding and streaming/webhook/async handling built into generated SDKs
- Terraform provider generation for infrastructure-as-code API integrations
ASEAN Perspective
Stainless in Southeast Asia
Stainless had no dedicated APAC presence, pricing in local currencies, or documented ASEAN customer base, though its generated SDKs — especially the OpenAI and Anthropic Python and TypeScript clients — are widely used by Southeast Asian AI developers daily. The service's abrupt shutdown in May 2026 disproportionately affects smaller APAC API teams that relied on its free tier or affordable Starter plan, as the leading alternatives (Speakeasy, Fern) carry higher entry-level pricing. APAC teams exploring SDK automation should evaluate Speakeasy or the open-source Stainful fork as migration paths.
Stainless set the industry bar for AI-generated SDK quality, powering the official libraries for OpenAI, Anthropic, Meta, and Google — a trust signal almost no competitor can match. Its compiler approach (using a custom stainless.yml DSL as an intermediary layer) produced genuinely idiomatic code across nine languages, with full CI/CD integration, automatic package-registry publishing, and changelog generation baked in. For API-first companies with multiple language targets, it removed weeks of repetitive boilerplate work on every API update.
The critical caveat as of 2026: the hosted service is shut down. Anthropic's acquisition in May 2026 ended access for new customers entirely, and existing customers lost automatic update workflows. Teams that built their SDK pipelines on Stainless must now migrate to an alternative or maintain generated SDKs manually. ASEAN and APAC teams also found limited regional support — no local data residency, documentation, or community presence in the region. The legacy verdict is outstanding capability; the current verdict is that you cannot buy it.
What people say
Stainless earned exceptional marks for capability and API output quality, with its compiler-grade approach producing genuinely idiomatic SDKs that senior engineers at OpenAI, Anthropic, and Cloudflare trusted for production use. Ease of use was strong for teams familiar with OpenAPI, though the custom stainless.yml DSL introduced a learning curve. Value was competitive on the free and Starter tiers. The fatal limitation as of mid-2026 is that the service no longer exists as a commercial product following Anthropic's $300M+ acquisition; ASEAN teams had no local presence or currency support beforehand.
Summary of public user & expert reviews, compiled by RECATOOLS.
Notable facts
- Stainless SDKs are downloaded tens of millions of times every week by developers worldwide — making it invisible infrastructure inside virtually every major AI app.
- Anthropic paid over $300 million for a company that had roughly $1 million in annual recurring revenue at the time of its seed round in April 2024 — a 300x+ revenue multiple reflecting strategic, not financial, value.
- The acquisition created an awkward situation: Anthropic now owns the tool that OpenAI and Google used to maintain their official developer libraries.
- Stainless used a custom YAML config layer (stainless.yml) between OpenAPI specs and generated code — a design decision that enabled fine-grained control but also locked customers into the platform's toolchain.
Frequently asked questions
About this listing
This entry was compiled from publicly available data including Stainless's official website, press releases, documentation, and reputable third-party publications. RECATOOLS is not affiliated with Stainless unless explicitly stated.
Third-party AI tools update their pricing, features, availability, and policies frequently. Information here may be outdated by the time you read this — we make reasonable efforts to keep listings current, but cannot guarantee absolute accuracy.
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