Anthropic Acquires Stainless to Enhance AI Developer Tooling

Anthropic, a leading artificial intelligence company, has acquired Stainless, a software startup founded in 2022 that develops software development kits (SDKs), command-line interfaces (CLIs), and MCP server tooling. This acquisition, announced on May 18, 2026, is designed to enhance the connectivity and developer experience of Anthropic’s Claude AI platform by integrating Stainless’ technology and engineering team.

Stainless has been instrumental in powering every official Anthropic SDK since the launch of its API. Its tools enable developers and AI agents to interact with APIs across multiple programming languages, including TypeScript, Python, Go, Java, and Kotlin. These SDKs and MCP servers are built to be fast, reliable, and feel native to each language, facilitating seamless integration and usage.

Katelyn Lesse, Head of Platform Engineering at Anthropic, commented, “Stainless has shaped how developers experience the Claude API since the start, and it’s been great to work with them on that. Agents are only as useful as what they can connect to. We’re excited to bring the Stainless team into Anthropic to advance Claude’s ability to connect to data and tools.” Alex Rattray, Founder and CEO of Stainless, added, “I started Stainless because SDKs deserve as much care as the APIs they wrap. Anthropic was one of the first teams to bet on this with us. Bringing our teams together was an easy decision, allowing us to continue our work on the platform where it matters most.”

The acquisition supports Anthropic’s broader strategy to push the frontier of AI agent connectivity. Anthropic developed the MCP (Modular Connectivity Protocol) to enable agents to connect with external data and tools effectively. By integrating Stainless’ expertise, Anthropic aims to accelerate SDK and tooling development cycles, improve reliability, and broaden language support.

Market trends show increasing demand for AI platforms that offer robust developer tools and seamless agent connectivity. This acquisition positions Anthropic to strengthen its competitive edge against other AI providers by enhancing the Claude platform’s integration capabilities. The deal also aligns with Anthropic’s partnership with PwC, which plans to roll out Claude Code and Cowork to U.S. teams and expand globally, training 30,000 professionals on the platform.

Financial terms of the acquisition were not disclosed. The deal involves a full acquisition of Stainless, with the startup’s team joining Anthropic to continue developing SDKs and MCP tooling. This internalization is expected to reduce third-party development costs and streamline platform engineering efforts.

Looking ahead, Anthropic plans to integrate Stainless’ technology fully into the Claude platform, enhancing agent connectivity and developer experience. The company will focus on maintaining SDK quality and scaling enterprise adoption through partnerships like PwC. Regulatory approvals were not mentioned, suggesting a smooth integration process.

Overall, this acquisition marks a significant step in Anthropic’s mission to expand AI agent capabilities and developer engagement, reinforcing its position in the AI developer tools market.