I Built openapi-mcp-gateway: Multi-Spec OpenAPI-to-MCP With Real OAuth2 In Python

This gateway started as a demo. The job was to turn our company's OpenAPI spec into an MCP server so non-technical product folks could try the API through Claude Desktop. The naive version came together quickly.

Then the demo grew. For a customer-support-style agent to be useful, it needed to chain our product API with the internal issue tracker, and both gate access on the user's identity, not a shared service token. The audience was non-technical, so streamable HTTP was the floor. But I did not know what the eventual production client would be, so I wanted stdio and SSE on the same binary as well.…