Founder @StainlessAPI, previously developer platform & products @Stripe

Joined November 2011
4 Photos and videos
Thank you @JenniferHli ! You're truly an investor like no other, and I'm deeply grateful to have had you on our board. Thank you for going with me on the crazy stuff, supporting me on the tough stuff, and pushing me on the important stuff - always with warmth & wisdom. So rare.
Huge congratulations to @RattrayAlex and the @StainlessAPI team on the acquisition by @AnthropicAI. From our earliest conversations, what stood out about Stainless was the clarity of the mission: make APIs feel effortless for developers, by turning API design into great SDKs, docs, and tooling by default. It sounds simple until you appreciate how much craft sits behind it. True to its name, Stainless polished every detail developers only notice when they’re missing: type safety, idiomatic clients, versioning, reliability, to create an experience that just works. That kind of infrastructure compounds. As AI becomes more programmable and more deeply embedded in every product, the interface between developers and models matters enormously. Stainless built one of the defining developer infrastructure companies for that world. Proud to have been part of the journey, and excited to see what the team builds next with Anthropic. Congrats Alex, Mark, Daniella, Alex A, Mirole and the entire Stainless team!!
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Alex Rattray retweeted
Anthropic is acquiring @stainlessapi, an SDK and MCP server platform that has powered every Anthropic SDK since the earliest days of our API. Read more: anthropic.com/news/anthropic…
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Alex Rattray retweeted
As @RattrayAlex taught me from his Stripe days: for most people is not about POST /v1/charges but stripe.charges.create(). That's how folks experience APIs.
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Thanks for having me on the podcast, @danshipper! Can't wait for the next one!
If your MCP server has dozens of tools, it’s probably built wrong. You need tools that are specific and clear for each use case—but you also can’t have too many. This creates an almost impossible tradeoff that most companies don’t know how to solve. That’s why I interviewed my friend Alex Rattray (@RattrayAlex), the founder and CEO of @StainlessAPI. Stainless builds APIs, SDKs, and MCP servers for companies like @OpenAI and @AnthropicAI. Alex has spent years mastering how to make software talk to software, and he came on the show to share what he knows. I had him on @every’s AI & I to talk about MCP and the future of the AI-native internet. We get into: • Design MCP servers to be lean and precise. Alex’s best practices for building reliable MCP servers start with keeping the toolset small, giving each tool a precise name and description, and minimizing the inputs and outputs the model has to handle. At Stainless, they also often add a JSON filter on top to strip out unnecessary data. • Make complex APIs manageable with dynamic mode. To solve the problem of how an AI figures out which tool to use in larger APIs, Stainless switches to “dynamic mode,” where the model gets only three tools: List the endpoints, pick one and learn about it, and then execute it. • MCP servers as business copilots. At Stainless, Alex uses MCP servers to connect tools like @NotionHQ and @HubSpot, so he can ask questions like, “Which customers signed up last week?” The system queries multiple databases and returns a summary that would’ve otherwise taken multiple logins and searches. • Create a “brain” for your company with Claude Code. Alex built a shared company brain at Stainless by keeping Claude Code running on his system and asking it to save useful inputs—like customer feedback and SQL queries—into GitHub. Over time, this creates a curated archive his team can query easily. • The future of MCP is code execution. Instead of giving models hundreds of tools, Alex believes the most powerful setup will be a simple code execution tool and a doc search tool. The AI writes code against an API’s SDK, runs it on a server, and checks the docs when it gets stuck. This is a must-watch for anyone who wants to understand MCP—and learn how to use them as a competitive edge. Watch below! Timestamps: Introduction: 00:01:14 Why Alex likes running barefoot: 00:02:54 APIs and MCP, the connectors of the new internet: 00:05:09 Why MCP servers are hard to get right: 00:10:53 Design principles for reliable MCP servers: 00:20:07 Scaling MCP servers for large APIs: 00:23:50 Using MCP for business ops at Stainless: 00:25:14 Building a company brain with Claude Code: 00:28:12 Where MCP goes from here: 00:33:59 Alex’s take on the security model for MCP: 00:41:10
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It's been an honor and a hoot working with @zeke & team at @replicate on their new SDKs & MCP server. Zeke was co-creator of the original Swagger specification (now OpenAPI) and has been a tremendously thoughtful & creative design partner for the tooling we now build on top of it 🙏
@replicate lets you run AI models with a cloud API, without having to understand machine learning or manage your own infra. Their first client libraries were hand-written, but became a maintenance burden as their HTTP API grew and evolved. The team wanted to transition to using an SDK generator, so they ran a thorough bake-off of Stainless against another provider. @zeke, Replicate’s founding designer and the co-creator of Swagger (now known as @OpenApiSpec), led the evaluation. Here are his words on what made Stainless stand out.
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Congrats @KaranVaidya6!! Been great collaborating w/ you and the team!
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Have so much more where this came from to make it easier for LLM's to interact fluidly with large API's over MCP! Thanks @zeke & @replicate team for being such a great design partner!
9 Jul 2025
Coming soon... snappier MCP interactions from @replicate's MCP server, thanks to dynamic `jq` filtering of API responses. 🤯 The team at @StainlessAPI really knows how to cook.
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Turns out there's a lot to explore at the frontier of MCP and agents using APIs -- and a lot of people excited to explore it! Thanks @danshipper, @mc_anthropic, @ilanbigio, @TomHacohen, and @shashankgoyal95 for dishing out the "warm takes" and hot ideas ♨️
12 Jun 2025
Last week, we hosted a panel discussion on "MCP and the future of AI x API" – and 150 engineers, founders, and product leaders packed our space to explore the future of agents & APIs. A special thanks to all the panelists: @danshipper - @every @ilanbigio - @OpenAI @mc_anthropic - @AnthropicAI @shashankgoyal95 - @openrouter @TomHacohen - @SvixHQ @RattrayAlex - @StainlessAPI Full recording below ⤵︎
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Alex Rattray retweeted
10 Jun 2025
ȀWe’re thrilled to be part of this year’s @Redpoint's InfraRed 100 list alongside our amazing customers building the infrastructure of tomorrow: @getmetronome, @browserbase, @scale_AI, @togethercompute, @gitpod, @composio, @OpenAI, and @AnthropicAI.
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Excited to see @cjbell_ & team at @knocklabs ship their 1.0 SDKs with @StainlessAPI !
Replying to @cjbell_
Next, we're shipping the 1.0 release of our Node, Go, Python, and Ruby SDKs. We partnered with @StainlessAPI to deliver these best-in-class SDKs that now include rich types, auto pagination, retries, customizable logging and more. They are a delight to use.
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Alex Rattray retweeted
You can now use Stainless to automatically generate MCP servers from your OpenAPI spec. It comes with built-in flags so your users can precisely control what gets exposed to the model: --tool --resource --operation --tag It's completely free and takes seconds to generate.
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Today, @StainlessAPI is announcing our Series A — more on why we’re building Stainless and what it means for developers:
10 Dec 2024
Excited to share that we’ve raised a $25M Series A, led by @JenniferHLi @a16z along with @sequoia, @thegp, @felicis, @zapier, and @mongoDB Ventures: stainlessapi.com/blog/stainl…
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Oh, and we’re hiring for roles across business, engineering, design, marketing and more: stainlessapi.com/jobs Help us build the platform that powers the internet’s most demanding APIs!

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Has been suuuper fun collaborating with @bterlson designing an open-source codegen system, github.com/alloy-framework/a…! It's been a delightful mix of "multiple discovery" of novel ideas, being wowed by Brian's magical solutions to impossible problems, and brainstorming sessions producing stuff I can't imagine either of us would have come up with alone. Codegen is a surprisingly hard, and very underinvested corner of computer science, and it's a special feeling to have a sense that we're pushing it forward.
Replying to @vuejs @solid_js
Also lots of folks have been giving great feedback along the way, e.g. the @TypeSpecLang crew (who will likely be using this for our upcoming emitter framework) and @RattrayAlex and the @StainlessAPI crew.
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Shoutout also to @twitchard from Stripe and Young-jin, @probablyrobert, and @mmcgrana from Stainless for poking on all the toughest edge-cases of "artisanal polyglot codegen" and building out the internal versions of this at @stripe and @StainlessAPI, respectively!
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Excited to see where things go from here!
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Honored to be a backer of @TigerBeetleDB ! Very excited to see where @jorandirkgreef and team take this technology next.
In 2020, we discovered a fundamental limit in the general-purpose DB design for transaction processing. This led to the creation of TigerBeetle. Today, I'm excited to announce TigerBeetle's $24 million Series A led by @natalievais of @sparkcapital. tigerbeetle.com/blog/2024-07…
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I'm sick of @Spotify's overzealous taste-bubbling and promotions. Which music streaming service should I switch to?
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Congrats to the @thegp on Fund 2!! They've been terrific partners to us at @StainlessAPI on many fronts.
NEWS: We’re proud to announce TheGP II, our $300M second fund. Our mission remains the same: we will keep redefining what partnership means between builders and investors by prioritizing service > scale.
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shipped a lil side project this weekend: copy/paste messages from Slack into other apps without absolutely losing your sanity over the formatting. rattrayalex-slack_cleaner.we… Thank you AI for writing most of the code and @ValDotTown for making hosting insanely easy 😊 It's probably full of bugs but feel free to try it out!

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