On May 18, 2026, Anthropic announced it has acquired Stainless, a company focused on SDKs, command-line tools (CLIs) and MCP server tooling. Anthropic said the acquisition aims to expand Claude agents' ability to connect to external systems and data.
What Stainless does
Stainless was founded in 2022 and has powered the generation of every official Anthropic SDK since the early days of Anthropic's API. The company converts API specifications into SDKs across multiple languages, including TypeScript, Python, Go, and Java. It also produces CLIs and MCP servers — the libraries, command-line tools, and connectors that let developers and agents use an API.
Anthropic's rationale and strategic importance
Katelyn Lesse, Head of Platform Engineering at Anthropic, said agents are only as useful as what they can connect to and noted that Stainless has shaped the developer experience around the Claude API from the start. Anthropic framed the acquisition as a way to advance Claude's ability to connect to data and tools by bringing the Stainless team in-house.
Stainless leadership and continuity
Alex Rattray, Founder and CEO of Stainless, said he started the company because SDKs deserve the same care as the APIs they wrap, and that Anthropic was an early supporter of that approach. Rattray added that watching what developers built on Claude made the decision to join forces easy. According to the announcement, the Stainless team will continue its work on the Anthropic platform after the acquisition.
MCP and the Claude Platform
Anthropic previously created MCP to enable agent connectivity. By combining the Stainless and Anthropic teams, the company intends to further the Claude Platform's developer experience and the range of systems agents can reach.
Summary
The acquisition formalizes an existing collaboration: Stainless has already been involved in generating Anthropic's SDKs. Anthropic says integrating Stainless' tooling will help produce faster, more reliable, and more idiomatic SDKs and connectors that improve how agents access external systems and data.
