OpenAPI to MCP Server: How to Turn REST APIs Into Reliable AI Tools Without Tool Bloat

OpenAPI to MCP Server If your company already has an API, the next question is obvious: can AI assistants use it safely without a developer writing custom glue for every workflow? That question became harder to ignore after Anthropic announced its acquisition of Stainless on May 18, 2026. Stainless is known for generating SDKs, CLIs, and MCP servers from API specs. The signal is not subtle. The API layer is becoming the tool layer for AI systems. But there is a trap. A raw OpenAPI-to-MCP conversion can make a look magical and a production system look confused.