Besides the focus on generative AI, what do AI startups like OpenAI, Anthropic, and Together AI have in common? They use Stainless, a platform created by Alex Rattray, formerly of Stripe, to generate SDKs for their APIs.
Rattray, who studied economics at the University of Pennsylvania, has been building things for as long as he can remember, from an underground newspaper in high school to a bike-share program in college. Rattray started programming on the side at UPenn, which led to a job at Stripe as an engineer on the developer platform team.
At Stripe, Rattray helped revamp the API documentation and launch the system that powers Stripe’s API client SDK. It was while working on these projects that Rattray observed that there was no easy way for companies, including Stripe, to create SDKs for their APIs at scale.
“The handwriting of the SDKs couldn’t scale,” he told TechCrunch. “Today, every API designer must once again address a million and one bikeshed questions and painstakingly ensure that those decisions are consistent across their entire API.
Now you might be wondering why would a company need an SDK if they offer an API? APIs are simply protocols that allow software components to communicate with each other and transfer data. SDKs, on the other hand, offer a set of software creation tools that connect to APIs. Without an SDK to accompany an API, API users are forced to read the API documentation and build everything themselves, which is not the best experience.
Rattray’s solution is Stainless, which integrates an API specification and generates SDKs in a range of programming languages, including Python, TypeScript, Kotlin, Go and Java. As APIs evolve and change, Stainless’s platform delivers these updates with versioning and changelog publishing options.
“API companies today have a team of several people building libraries in each new language to plug into their API,” Rattray said. “These libraries inevitably become inconsistent, obsolete and require constant changes from specialist engineers. Stainless solves this problem by generating them via code.
Stainless is not the only API to SDK generator. There’s LibLab and Speakeasy, to name a few, as well as long-running open source projects such as OpenAPI Generator.
Stainless, however, offers more “polish” than most, Rattray said, thanks in part to its use of generative AI.
“Stainless uses generative AI to produce an initial ‘Stainless configuration’ for customers, which it is then up to them to refine their API,” he explained. “This is particularly valuable for AI companies, whose huge user bases include many novice developers trying to integrate complex features like streaming and chat tools.”
This may be what attracted customers like OpenAI, Anthropic, and Together AI, as well as Lithic, LangChain, Orb, Modern Treasury, and Cloudflare. Stainless has “dozens” of paying customers in its beta, Rattray said, and some of the SDKs it has generated, including OpenAI’s Python SDK, receive millions of downloads per week.
“If your business wants to become a platform, your API is the foundation,” he said. “Perfect SDKs for your API enable faster integration, wider feature adoption, faster upgrades, and confidence in the quality of your engineering. »
Most customers pay for Stainless’s enterprise tier, which includes additional services and AI-specific features. Publishing a single SDK with Stainless is free. But companies have to pay between $250 per month and $30,000 per year for multiple SDKs in multiple programming languages.
Rattray started Stainless “with revenue from day one,” he said, adding that the company could be profitable as soon as this year; annual recurring revenue hovers around $1 million. But Rattray instead chose to call on external investment to create new product lines.
Stainless recently closed a $3.5 million seed round with participation from Sequoia and The General Partnership.
“Across the tech ecosystem, Stainless stands out as a model that elevates the developer experience, rivaling the high standards once set by Stripe,” said Anthony Kline, partner at The General Partnership. “As APIs continue to be the building blocks for integrating services like LLMs into applications, Alex’s direct experience pioneering Stripe’s API code generation system positions him to unique way to make Stainless the ultimate platform for transparent, high-quality API interactions.
Stainless has a team of 10 people based in New York. Rattray expects the headcount to reach 15 or 20 people by the end of the year.
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