Besides a focus on generative AI, what do AI startups like OpenAI, Anthropic, and Together AI have in common? They use Stainless, a platform created by former Stripe staffer Alex Rattray, to build API I am generating an SDK for.
Mr. Rattray, who studied economics at the University of Pennsylvania, has been creating things for as long as he can remember, from an underground newspaper in high school to a bike-sharing program in college. Rattray learned programming on the side during his time at UPenn, which led to a job as an engineer on his team for Stripe's developer platform.
At Stripe, Rattray helped revamp API documentation and launch a system to power Stripe's API client SDK. While working on these projects, Rattray realized there was no easy way for companies, including Stripe, to build their own SDKs for his API at scale.
“We couldn't scale with a hand-written SDK,” he told TechCrunch. “Today, every API designer must once again solve a million “bike storage” questions and painstakingly enforce consistency around these decisions across the API. ”
Now, you may be wondering why you need an SDK if your company provides an API. An API is simply a protocol that allows software components to communicate with each other and transfer data. An SDK, on the other hand, provides a set of software creation tools that plug into the API. If your API doesn't come with her SDK, API users will have to read her API documentation and build everything themselves, which isn't the best experience.
Rattray's solution is stainless steel that takes an API specification and generates an SDK in a variety of programming languages, including Python, TypeScript, Kotlin, Go, and Java. As APIs evolve and change, Stainless' platform pushes those updates using version control and changelog publishing options.
“Today's API companies have teams of several people building libraries for each new language to connect to their APIs,” says Rattray. “These libraries inevitably become inconsistent, outdated, and require constant modification by specialized engineers. Stainless solves that problem by generating it through code. ”
Stainless isn't the only API-to-SDK generator. In addition to LibLab and Speakeasy, there are also long-standing open source projects such as OpenAPI Generator.
But Stainless will be “more sophisticated” than most other products, Rattray said, thanks to the use of generative AI.
“Stainless uses generative AI to create an initial ‘Stainless config’ for the customer, who then fine-tune it to the API,” he explained. “This is especially valuable for AI companies with large user bases that often include novice developers looking to integrate with complex features such as chat streaming and tools.”
Perhaps that's what attracted customers like OpenAI, Anthropic, and Together AI, as well as Lithic, LangChain, Orb, Modern Treasury, and Cloudflare. Rattray said Stainless has “dozens” of paid clients in beta, and some of his SDKs that Stainless produces, such as his Python SDK for OpenAI, are downloaded in the millions every week.
“If your company wants to be a platform, APIs are the foundation for that,” he said. “The best SDKs for APIs facilitate faster integration, broader feature adoption, faster upgrades, and confidence in engineering quality.”
Most customers pay for the stainless steel enterprise tier, which comes with additional white glove services and AI-specific features. Publishing a single SDK on Stainless is free. But companies must pay anywhere from $250 per month to $30,000 per year for multiple SDKs across multiple programming languages.
Rattray launched Stainless Steel itself and it has been “profitable from day one,” he said, adding that it could be profitable as early as this year. Annual recurring revenue hovers around $1 million. However, Rattray instead chose to accept outside investment to build a new product line.
Stainless recently closed a $3.5 million seed round with participation from Sequoia and General Partnership.
“Across the technology ecosystem, Stainless stands out as a beacon for improving the developer experience, matching the high standards once set by Stripe,” said Anthony Kline, Partner at The General Partnership. states. “Alex's first-hand experience pioneering Stripe's API code generation system allows us to create seamless, high-quality API interactions, as APIs continue to be the core building block for integrating services such as his LLM into applications. We are in a unique position to incorporate stainless steel into typical platforms for
Stainless has a team of 10 people based in New York. Rattray expects the number of employees to grow to 15 or 20 by the end of the year.