Alex Rattray, founder of Stainless, is on a mission to revolutionize the way software development kits (SDKs) are created and used. Rattray believes that AI can assist in generating SDKs from APIs, making it easier for developers to create apps using various products. This vision has attracted significant attention, with Stainless recently closing a $25 million Series A funding round led by a16z, with participation from Sequoia, The General Partnership, Felicis, Zapier, and MongoDB.
The problem Stainless is trying to solve is that many vendors only offer APIs, which are simply protocols that enable software components to communicate with each other. Without an SDK, API users are forced to read API documentation and build everything themselves, a time-consuming and labor-intensive process. Stainless' platform uses AI to generate SDKs from APIs automatically, largely on the fly, in a range of programming languages including Python, TypeScript, Kotlin, and Go.
As APIs evolve and change, Stainless' platform pushes those updates with options for versioning and publishing changelogs. This approach avoids problems like libraries becoming inconsistent or outdated, and can drive quicker upgrades and faster time to integration. Rattray asserts that this will become increasingly important as APIs grow from a power-user feature to a primary interface for all users, and companies without excellent APIs will become as anachronistic as a restaurant without a website.
Rattray's experiences in the industry informed much of Stainless' functionality. As an economics major who picked up programming on the side, Rattray landed a job at Stripe as an engineer on the developer platform team, where he helped revamp API documentation and launch the system that powers Stripe's API client SDK. This background has given him a unique perspective on the challenges of API development and the potential of AI to simplify the process.
Stainless isn't the only API-to-SDK generator out there, with competitors like LibLab and Speakeasy, as well as longstanding open-source projects such as the OpenAPI Generator. However, Rattray argues that Stainless delivers more "polish" thanks to its AI-powered approach, which sets it apart from other solutions. Many customers have reportedly tried other options, including the OpenAPI Generator, but found them to fall short on code quality, requiring significant editing to bring the output up to standard.
Stainless' platform has already attracted a impressive roster of customers, including tech giants like OpenAI, Anthropic, and Meta, as well as Runway, Groq, Cerebras, Modern Treasury, and Cloudflare. The company claims to have "hundreds" of paying customers, with its SDKs being downloaded tens of millions of times every week. Most customers are paying for Stainless' enterprise tier, which comes with additional white-glove services and AI-specific functionality.
The new funding will be used to expand Stainless' 20-person team, with the company nearing profitability and annual recurring revenue hovering around $1 million. Rattray says that the business is very efficient, but the company decided to raise to accelerate development toward its vision of building a comprehensive platform developers turn to for everything API-related. With this latest funding round, Stainless has brought its total raised to ~$35 million.
As the API economy continues to grow, Stainless is well-positioned to capitalize on the trend. With its AI-powered SDK generator, the company is simplifying API development and making it easier for developers to create apps using various products. As Rattray notes, "We're quickly entering a world where everyone has access to an expert-level engineer in their pocket," and Stainless is at the forefront of this shift.