Anthropic Buys Stainless to Strengthen AI Developer Tools

The deal brings SDK and MCP server tooling in-house as Anthropic pushes deeper into agent infrastructure.

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  • Anthropic on Monday said it has acquired Stainless, a New York-based developer tools startup, as the artificial intelligence company expands the software infrastructure that helps agents connect to external systems.

    Financial terms were not disclosed. The Information reported last week that Anthropic was in talks to buy Stainless for more than $300 million.

    Founded in 2022 by Alex Rattray, Stainless builds tools that turn API specifications into software development kits, command-line tools and MCP servers. Its products generate SDKs across languages including TypeScript, Python, Go, Java and Kotlin.

    Anthropic said Stainless has generated every official Anthropic SDK since the early days of its API. Hundreds of companies use Stainless to generate SDKs, CLIs and MCP servers, the company said.

    “Stainless has shaped how developers experience the Claude API since the start, and it’s been great to work with them on that,” Katelyn Lesse, Anthropic’s head of platform engineering, said in the statement. “Agents are only as useful as what they can connect to.”

    Stainless said it will wind down all hosted products, including its SDK generator, as it focuses on Claude Platform capabilities and agent connectivity. 

    New signups, projects and SDKs are no longer available. Existing customers will retain ownership of SDKs already generated and can modify or extend them.

    The move brings a widely used developer infrastructure layer inside Anthropic. 

    TechCrunch reported that Stainless software has been used by companies including OpenAI, Google, Replicate, Runway and Cloudflare, making the acquisition notable for Anthropic’s competitors as well as its own platform.

    “I started Stainless because SDKs deserve as much care as the APIs they wrap,” Rattray said. “Anthropic was one of the first teams to bet on this with us.”

    The acquisition comes as AI companies shift more attention from chatbot interfaces to agents that can connect with enterprise systems, tools and data sources.

    Anthropic said the deal will help advance Claude’s ability to connect to data and tools, because apparently even artificial intelligence now needs better plumbing before it can act useful.

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