Anthropic announced on May 18 that it has acquired Stainless, a New York-based startup whose SDK generation and MCP server tooling is used by OpenAI, Google, Cloudflare, Replicate, and Runway, according to TechCrunch. The deal is worth more than $300 million, per The Information’s earlier reporting cited by TechCrunch.
Anthropic will wind down all hosted Stainless products, including the SDK generator, according to TechCrunch. Existing customers retain full ownership and modification rights to SDKs they have already generated, but the platform itself is gone. Going forward, the tooling is exclusive to Anthropic.
What Stainless Does
Stainless, founded in 2022 by former Stripe engineer Alex Rattray, automates the creation and maintenance of software development kits across Python, TypeScript, Kotlin, Go, and Java, per TechCrunch. The platform takes API specifications and produces production-ready SDKs that automatically update as APIs change.
According to Anthropic’s announcement, Stainless software has powered every official Anthropic SDK since the earliest days of its API. The company was backed by Sequoia Capital and Andreessen Horowitz, per TechCrunch.
“I started Stainless because SDKs deserve as much care as the APIs they wrap,” Rattray said in Anthropic’s press release. “Anthropic was one of the first teams to bet on this with us.”
Why It Matters for Agent Infrastructure
The acquisition removes a shared infrastructure layer from the agent ecosystem. Stainless is particularly valuable to companies building AI agents that connect to external software, because agents need reliable, auto-updating SDK integrations to call third-party APIs, according to TechCrunch. By acquiring Stainless and shutting down hosted access, Anthropic gains a structural advantage: Claude agents get native, maintained SDK tooling while competitors must build or source their own.
The MCP server tooling component is equally significant. As the Model Context Protocol becomes a standard interface for agent-to-service communication, controlling the tooling that generates MCP servers gives Anthropic leverage over how quickly and reliably third-party services become accessible to Claude agents.
OpenAI, Google, and Cloudflare now need to either build equivalent SDK infrastructure internally, find an alternative vendor, or fork the existing generated code and maintain it themselves, as WinBuzzer reported.