Most teams already have hundreds of internal APIs described in OpenAPI, but very few have the time or budget to hand build MCP servers for all of them. In this session, I will show how to take a real OpenAPI 3.1 specification and generate a working MCP server using open source tooling. The generated server includes Streamable HTTP transport, tool discovery, and typed input validation, giving agents a discoverable, invocable interface without writing MCP specific code.

The demo, however, is only the starting point. The core of the talk explains how OpenAPI operations map to MCP tools, how request and response schemas become typed tool inputs and outputs, and how HTTP failures can be translated into structured MCP errors that agents can handle programmatically. From there, we will examine the practical issues that make generated servers fail in production, including pagination, file uploads, polymorphic responses, auth propagation, and tool name collisions.

I will also show the tuning needed to make these servers dependable in real environments, including naming cleanup, schema refinement, auth handling, and guardrails for agent usability. The session concludes with a Spring Boot Gradle plugin that fits into an existing CI pipeline and a decision matrix for choosing which APIs are the best candidates for conversion first. Attendees will leave with a repeatable pipeline, a working example, and a clear framework for scaling MCP adoption across large API portfolios.