Anthropic Acquires SDK Startup Stainless for Over $300 Million, Expanding Control Over Its AI Toolchain

AIMPACT News, May 19 (UTC+8): According to monitoring by Beating, Anthropic has officially acquired the developer tools startup Stainless. Stainless specializes in using AI to automatically package complex APIs into cross-language SDKs. Following the acquisition, the entire Stainless team will be integrated into Anthropic to focus specifically on connecting Claude with external tools and data. This transaction effectively gives Anthropic direct control over the underlying toolchain of its competitors. Due to the high engineering costs of maintaining multi-language SDKs internally, OpenAI previously abandoned in-house development and fully shifted to Stainless. Although alternative solutions such as Speakeasy and LibLab exist, all three leading large model providers—OpenAI, Google, and Anthropic—currently rely on Stainless to generate their SDKs. The exact transaction amount has not been publicly disclosed. However, according to prior disclosures by The Information, the acquisition price was at least $300 million, effectively doubling Stainless’s $150 million valuation from last December. In addition to serving the three major model providers, Stainless previously developed dedicated tools for Anthropic’s released MCP (Model Context Protocol). This marks Anthropic’s fourth acquisition in six months: following its purchase of the JavaScript runtime Bun last year, it has since acquired the computer operation firm Vercept and the AI biotech company Coefficient Bio. (Source: BlockBeats)