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OpenAPI MCP Server

CLI tool to create an MCP server exposing services from an OpenAPI specification

Installation

Add the following to your MCP client configuration file.

Configuration

{
  "mcpServers": {
    "jaceromri-openapi-mcp-proxy": {
      "command": "npx",
      "args": [
        "openapi-mcp-proxy",
        "--spec",
        "./path/to/openapi.yml",
        "--target",
        "http://your-api.com",
        "--port",
        "3000"
      ],
      "env": {
        "PORT": "3000",
        "OMP_TARGET_BASE_URL": "https://petstore.swagger.io/v2",
        "OMP_OPENAPI_SPEC_FILE": "./path/to/openapi.yml"
      }
    }
  }
}

You can transform any OpenAPI service into an MCP server so AI agents and tools that understand Model Context Protocol can discover and interact with your REST API without modifying the service itself. This proxy translates between MCP and REST, letting you expose existing OpenAPI-described endpoints to MCP clients.

How to use

Start an MCP server for your OpenAPI service by pointing the proxy to your OpenAPI spec, the actual API target, and the port you want the MCP interface to listen on.

Common usage pattern looks like this, where you provide your API spec and target, and choose a port for the MCP endpoint.

npx openapi-mcp-proxy --spec ./path/to/openapi.yml --target http://your-api.com --port 3000

MCP testing and integration

To verify the MCP server is responding as expected, you can use the MCP Inspector and VS Code integration to interact with the server and see the available MCP endpoints.

MCP Inspector lets you connect to your server’s MCP endpoint (ending with /mcp) and inspect requests and responses in a UI.

VS Code integration allows you to add your MCP server to the agent mode and interact with it directly from the editor.

# Install MCP Inspector
npx @modelcontextprotocol/inspector

# Start your MCP server (example shown above)
# Open the inspector UI at the server path ending with /mcp, e.g. http://localhost:3000/mcp

OpenAPI example

An example setup uses a Petstore OpenAPI spec to expose the API via MCP.

npx openapi-mcp-proxy --spec resources/petstore.openapi.yml --target https://petstore.swagger.io/v2

Available tools

mcp_inspector

A CLI/UI tool to test and inspect MCP servers, showing requests and responses.

vscode_agent_integration

VS Code integration to add MCP servers to the built-in agent mode for interactive usage.