Anthropic Acquires Stainless to Bolster SDK and MCP Tooling for Agents

Anthropic is buying Stainless, the developer-tools company that has generated every official Anthropic SDK since the company’s earliest API days. Founded in 2022, Stainless converts API specs into idiomatic client libraries across TypeScript, Python, Go, Java, and Kotlin, and also produces CLIs and MCP servers used by hundreds of companies to expose APIs to both human developers and AI agents.

The acquisition is framed around agent connectivity: Anthropic’s pitch is that autonomous agents are bottlenecked by the quality of the tooling that lets them reach external systems, and Stainless’s code-generation pipeline is the most direct lever for improving that surface area. The Stainless team will continue its existing work, now folded into Anthropic’s Claude Platform group under Head of Platform Engineering Katelyn Lesse.

The move tightens Anthropic’s grip on the developer-experience layer around Claude and on MCP, the protocol Anthropic introduced to standardize agent-to-tool connections. Terms were not disclosed, and there is no public statement on whether Stainless will continue serving competing model providers whose SDKs it currently generates.