Anthropic Acquires Stainless to Vertically Integrate SDK and MCP Ecosystem

Internalizing Core Infrastructure for Agent Connectivity

Anthropic has acquired Stainless, the SDK and MCP server platform that has powered every official Anthropic SDK since the earliest days of the API. Stainless transforms API specifications into SDKs across TypeScript, Python, Go, Java, Kotlin, and other languages — and was also used by OpenAI, Google, Cloudflare, and other major tech companies.

Deal Valued at Over $300 Million

According to The Information, the acquisition price is believed to exceed $300 million. The deal marks Anthropic's fourth acquisition in six months: Bun (JavaScript runtime, December 2025), Vercept (computer use agents, February 2026), Coefficient Bio (biotech AI, April 2026), and now Stainless (May 2026).

Stainless Hosted Products Shutting Down

Following the acquisition, Stainless will wind down all hosted products, including its SDK generator, CLI tools, and MCP server generation service. Existing customers retain full ownership of their generated SDKs and are free to modify and extend them.

Vertical Integration of the Agent Stack

Anthropic's acquisition spree is a deliberate vertical integration strategy across every layer of the agent stack: the runtime (Bun), autonomous operation (Vercept), domain applications (Coefficient Bio), and now connectivity (Stainless). This acquisition significantly strengthens Anthropic's control over the MCP ecosystem — a protocol Anthropic itself created.