OpenAPI to MCP Converter

From an OpenAPI document to a working MCP server

Paste an OpenAPI (or Swagger) JSON document above and this converter maps every operation to an MCP tool: the operation becomes the tool name, its summary becomes the description a model reads, and the path, query and body parameters are flattened into a single JSON input schema. You get the tool definitions on their own, plus a FastMCP Python server built around them that runs as soon as you add authentication.

The whole conversion happens in your browser. No request is made, nothing is uploaded, and nothing is stored — which matters, because an OpenAPI document is very often a description of an internal API that has no business being pasted into somebody else's server. You can verify that in your browser's network tab.

The mistake almost everyone makes first

Converting all of an API is the obvious move and it is usually the wrong one. An MCP server's tool definitions are sent to the model on every single turn, so eighty endpoints become eighty descriptions and eighty schemas in the context window of every request — and the model's ability to pick the right one falls sharply as that list grows.

Start with the handful of operations an agent genuinely needs. Add more only when something turns out to be missing. You can measure exactly what a given tool list costs with the MCP token calculator.

What the generated code does and does not do

• Authentication is not included. The scaffold calls your API with no credentials; wiring in the header, token or OAuth flow is yours to add.
• Path parameters are placeholders. They are interpolated into the request path, but check each one substitutes the argument you expect.
• Request bodies behind a $ref are emitted as a generic object rather than expanded, because resolving them needs the components section. Flagged in the output rather than dropped quietly.
• JSON only. A YAML parser cannot be loaded here without a third-party script, and this site loads none. Export your spec as JSON first — most tooling does it in one command.

Related tools and guides

• Turn a REST API into an MCP server — the full walkthrough, including auth and deployment.
• MCP Inspector — once it is deployed, confirm it exposes what you expect.
• MCP Security Scanner — a converted API often inherits parameters worth a second look.
• Securing an MCP server

A generated server is a starting point, not a demo

Running it proves the mapping worked. It does not help anyone else understand what the server is for — and a customer evaluating your MCP integration cannot read a Python file. Deploy it, point MCP Showcase at the URL, and you get a live playground with generated documentation per tool, where a prospect can try the thing in a browser instead of taking your word for it.