Anthropic: Acquiring Stainless integrates MCP server tooling and SDK development directly into the Claude platform

On May 18, 2026, Anthropic announced the acquisition of Stainless as a strategic investment in AI agent infrastructure — a move that directly strengthens Claude’s ability to connect to third-party data and tools.

Anthropic acquires Stainless — the company behind all official SDKs

Anthropic announced on May 18, 2026 the acquisition of Stainless, a specialized provider of tools for automatically generating SDKs (Software Development Kits — software interfaces that developers use to integrate with APIs) and MCP servers (Model Context Protocol — a standardized protocol through which AI agents access external data and tools).

Stainless was founded in 2022 under the leadership of Alex Rattray. From the very beginning of the Anthropic API, the company was responsible for building and maintaining all official Anthropic SDKs for TypeScript, Python, Go, Java, Kotlin and additional programming languages. In addition to SDKs, Stainless delivers CLI tools (command-line interfaces) that help development teams test API integrations. Upon the announcement, Rattray stated that “SDKs deserve just as much care as the APIs they wrap.”

How does Anthropic plan to use Stainless technology?

Anthropic states in its announcement that “agents are only as useful as their ability to connect to data and tools.” Stainless technology directly addresses that problem — the company builds MCP servers that give Claude agents access to external APIs, databases and third-party systems without the need to manually write integration code.

Katelyn Lesse, Head of Platform Engineering at Anthropic, notes that the acquisition strengthens Claude’s ecosystem and agent functionality. Hundreds of companies already use Stainless for automated SDK creation — each SDK is described as fast, reliable and written to feel native in its programming language. Merging the Stainless team with Anthropic’s engineers should accelerate development of new language targets and reduce the lag between new API capabilities and their availability in SDKs.

What does this acquisition change for the MCP ecosystem?

MCP is the protocol Anthropic launched to standardize connecting AI agents to external data sources and business tools. Stainless already built the infrastructure powering MCP server tooling, which means Anthropic now internally controls the entire chain — from protocol design to the tools that implement that protocol for hundreds of third parties.

For developers building on Claude, the acquisition potentially means better-integrated SDKs, faster MCP server updates alongside new model versions, and closer API-SDK parity. The Stainless team moves to Anthropic and continues working on the same technology foundation as part of the infrastructure that directly supports the Claude platform. Companies that used Stainless for their own SDKs can expect continuity of service. Financial terms of the acquisition were not disclosed.