OpenAPI MCP server

Dynamically generates tools from OpenAPI specifications, enabling seamless interaction with a wide range of RESTful APIs for flexible service integration and rapid prototyping.
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Setup instructions
Provider
Ross Masters
Release date
Feb 23, 2025
Language
Python
Package
Stats
1.6K downloads
8 stars

This MCP-OpenAPI server allows you to expose HTTP methods from an OpenAPI specification as tools that can be used by LLMs through the Model Context Protocol (MCP). It acts as a bridge between LLMs and existing APIs defined by OpenAPI specs.

Installation

You can install the MCP-OpenAPI server from PyPI:

pip install mcp-openapi

The server requires uvx to run.

Running the Server

There are two ways to run the MCP-OpenAPI server: using SSE (Server-Sent Events) or stdio mode.

Basic Usage

Start the server by specifying an OpenAPI URL and the mode:

uvx mcp-openapi --openapi-url https://httpbin.org/spec.json sse

or

uvx mcp-openapi --openapi-url https://httpbin.org/spec.json stdio

Configuration Options

You can configure the server using command-line arguments or environment variables:

OpenAPI URL:

  • Command line: --openapi-url=URL
  • Environment variable: MCP_OPENAPI_URL

SSE Mode Configuration:

  • --fastmcp-sse-host - the host to serve the MCP server on
  • --fastmcp-sse-port - the port to serve the MCP server on

Global Options:

  • --fastmcp-debug - enable debug mode for the MCP server
  • --fastmcp-log-level - the log level for the MCP server

These can also be configured via environment variables using the FASTMCP_ prefix, e.g., FASTMCP_LOG_LEVEL=DEBUG.

Integrating with an LLM

Here's an example of how to integrate the MCP-OpenAPI server with Claude:

{
  "mcpServers": {
    "todos": {
      "command": "uvx",
      "args": [
        "mcp-openapi",
        "--openapi-url=http://localhost:8000/openapi.json",
        "stdio"
      ]
    }
  }
}

API Authentication

MCP-OpenAPI can use a global auth token when making requests to the target API:

uvx mcp-openapi --openapi-url=URL --auth-token=YOUR_TOKEN stdio

The token will be used as a bearer token or for basic authentication depending on the OpenAPI spec.

Supported OpenAPI Versions

MCP-OpenAPI supports:

  • ✅ OpenAPI 3.0
  • ✅ OpenAPI 3.1
  • ❌ Swagger 2.0

Both JSON and YAML formats are supported.

How It Works

  1. The server initializes with an OpenAPI spec URL
  2. It fetches and parses the spec, registering each path-operation as a tool
  3. A FastMCP server starts with the registered tools
  4. When a client requests a tool, the MCP server makes an HTTP request to the API and returns the response

How to install this MCP server

For Claude Code

To add this MCP server to Claude Code, run this command in your terminal:

claude mcp add-json "todos" '{"command":"uvx","args":["mcp-openapi","--openapi-url=http://localhost:8000/openapi.json","stdio"]}'

See the official Claude Code MCP documentation for more details.

For Cursor

There are two ways to add an MCP server to Cursor. The most common way is to add the server globally in the ~/.cursor/mcp.json file so that it is available in all of your projects.

If you only need the server in a single project, you can add it to the project instead by creating or adding it to the .cursor/mcp.json file.

Adding an MCP server to Cursor globally

To add a global MCP server go to Cursor Settings > Tools & Integrations and click "New MCP Server".

When you click that button the ~/.cursor/mcp.json file will be opened and you can add your server like this:

{
    "mcpServers": {
        "todos": {
            "command": "uvx",
            "args": [
                "mcp-openapi",
                "--openapi-url=http://localhost:8000/openapi.json",
                "stdio"
            ]
        }
    }
}

Adding an MCP server to a project

To add an MCP server to a project you can create a new .cursor/mcp.json file or add it to the existing one. This will look exactly the same as the global MCP server example above.

How to use the MCP server

Once the server is installed, you might need to head back to Settings > MCP and click the refresh button.

The Cursor agent will then be able to see the available tools the added MCP server has available and will call them when it needs to.

You can also explicitly ask the agent to use the tool by mentioning the tool name and describing what the function does.

For Claude Desktop

To add this MCP server to Claude Desktop:

1. Find your configuration file:

  • macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
  • Windows: %APPDATA%\Claude\claude_desktop_config.json
  • Linux: ~/.config/Claude/claude_desktop_config.json

2. Add this to your configuration file:

{
    "mcpServers": {
        "todos": {
            "command": "uvx",
            "args": [
                "mcp-openapi",
                "--openapi-url=http://localhost:8000/openapi.json",
                "stdio"
            ]
        }
    }
}

3. Restart Claude Desktop for the changes to take effect

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