Tidewell Software

Free tool · runs in your browser

OpenAPI to MCP converter

Paste an OpenAPI 3.0 or 3.1 schema, for example the one behind a custom GPT Action, and see it as MCP tools: names, arguments, and read-only or destructive hints from each HTTP method. Then download a complete MCP server (Cloudflare Worker or Node.js, with a README) for free. Everything runs in your browser; nothing is uploaded.

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What the converter does

  • Resolves $ref references, merges allOf bodies, converts OpenAPI 3.0 nullable and exclusive bounds to JSON Schema 2020-12, and drops readOnly fields from request bodies.
  • Names tools from operationId (letters, digits, _ and -, up to 64 characters, which every major client accepts).
  • Flattens JSON bodies into tool arguments when the names do not clash, so assistants fill them in reliably.
  • Hides parameters that the API key already supplies, so the model never sees or invents them.

The downloaded server

A small, dependency-free MCP server over Streamable HTTP that answers both MCP protocol eras (2026-07-28 and 2024-11-05 to 2025-11-25). API credentials come from environment variables, and an optional MCP_ACCESS_TOKEN protects the endpoint. Deploy the Worker with npx wrangler deploy or run the Node version with node server.mjs. MIT licence.

Prefer not to host it? ActionBridge runs the same server for you, with encrypted credentials and OAuth for ChatGPT and Claude. Migrating a GPT? Read how to migrate custom GPT Actions to MCP.

Third-party code: yaml by Eemeli Aro (ISC licence), bundled into the converter script.

Frequently asked questions

Is my schema uploaded?

No. The schema is parsed, converted and packaged into the ZIP in your browser. The page has no analytics and its security policy blocks it from sending data anywhere.

Which OpenAPI versions work?

OpenAPI 3.0 and 3.1 in JSON or YAML. Swagger 2.0 must be converted to OpenAPI 3 first.

Does it support authentication?

Yes: none, API key (header or query), bearer, basic and OAuth client credentials in the self-host code. Per-user OAuth needs an OAuth server; the self-host code forwards the client's own bearer token instead, and the hosted ActionBridge runs the full sign-in.

What is MCP?

The Model Context Protocol, the open standard that ChatGPT plugins, Claude connectors, Cursor and VS Code use to call external tools.

Last updated 8 November 2026. Questions or corrections: [email protected].