Anthropic Acquires SDK Toolmaker Stainless for at Least $300 Million to Bolster AI Infrastructure

Stainless was founded in 2022 by former Stripe engineer Alex Rattray. Its technology automatically converts API specifications into SDKs, CLIs and MCP servers in multiple programming languages. Its customers include OpenAI, Google and Meta, and it has long generated Anthropic’s official SDKs, making it key infrastructure for connecting AI agents to data and third-party services.

Anthropic announced its acquisition of Stainless on May 18, 2026, without disclosing the terms. The Information previously reported that the deal was worth at least $300 million. The Stainless team will join Anthropic to strengthen development tools and agent connectivity for the Claude platform. Existing customers will retain ownership of their generated SDKs and the right to modify and extend them.