mcp-openapi-proxy

mcp-openapi-proxy is a Python package that implements a Model Context Protocol (MCP) server, designed to dynamically expose REST APIs—defined by OpenAPI specifications—as MCP tools. This facilitates seamless integration of OpenAPI-described APIs into MCP-based workflows.

Table of Contents

• Overview
• Features
• Installation
  • MCP Ecosystem Integration
• Modes of Operation
  • FastMCP Mode (Simple Mode)
  • Low-Level Mode (Default)
• Environment Variables
• Examples
  • Glama Example
  • Fly.io Example
  • Render Example
  • Slack Example
  • GetZep Example
  • Virustotal Example
  • Notion Example
  • Asana Example
  • APIs.guru Example
  • NetBox Example
  • Box API Example
  • WolframAlpha API Example
• Troubleshooting
• License

Overview

The package offers two operational modes:

• Low-Level Mode (Default): Dynamically registers tools corresponding to all valid API endpoints specified in an OpenAPI document (e.g. /chat/completions becomes chat_completions()).
• FastMCP Mode (Simple Mode): Provides a streamlined approach by exposing a predefined set of tools (e.g. list_functions() and call_function()) based on static configurations.

Features

• Dynamic Tool Generation: Automatically creates MCP tools from OpenAPI endpoint definitions.
• Simple Mode Option: Offers a static configuration alternative via FastMCP mode.
• OpenAPI Specification Support: Compatible with OpenAPI v3 with potential support for v2.
• Flexible Filtering: Allows endpoint filtering through whitelisting by paths or other criteria.
• Payload Authentication: Supports custom authentication via JMESPath expressions (e.g. for APIs like Slack that expect tokens in the payload not the HTTP header).
• Header Authentication: Uses Bearer by default for API_KEY in the Authorization header, customizable for APIs like Fly.io requiring Api-Key.
• MCP Integration: Seamlessly integrates with MCP ecosystems for invoking REST APIs as tools.

Installation

Install the package directly from PyPI using the following command:

MCP Ecosystem Integration

To incorporate mcp-openapi-proxy into your MCP ecosystem configure it within your mcpServers settings. Below is a generic example:

Refer to the Examples section below for practical configurations tailored to specific APIs.

Modes of Operation

FastMCP Mode (Simple Mode)

• Enabled by: Setting the environment variable OPENAPI_SIMPLE_MODE=true.
• Description: Exposes a fixed set of tools derived from specific OpenAPI endpoints as defined in the code.
• Configuration: Relies on environment variables to specify tool behavior.

Low-Level Mode (Default)

• Description: Automatically registers all valid API endpoints from the provided OpenAPI specification as individual tools.
• Tool Naming: Derives tool names from normalized OpenAPI paths and methods.
• Behavior: Generates tool descriptions from OpenAPI operation summaries and descriptions.

Environment Variables

• OPENAPI_SPEC_URL: (Required) The URL to the OpenAPI specification JSON file (e.g. https://example.com/spec.json or file:///path/to/local/spec.json).
• OPENAPI_LOGFILE_PATH: (Optional) Specifies the log file path.
• OPENAPI_SIMPLE_MODE: (Optional) Set to true to enable FastMCP mode.
• TOOL_WHITELIST: (Optional) A comma-separated list of endpoint paths to expose as tools.
• TOOL_NAME_PREFIX: (Optional) A prefix to prepend to all tool names.
• API_KEY: (Optional) Authentication token for the API sent as Bearer <API_KEY> in the Authorization header by default.
• API_AUTH_TYPE: (Optional) Overrides the default Bearer Authorization header type (e.g. Api-Key for GetZep).
• STRIP_PARAM: (Optional) JMESPath expression to strip unwanted parameters (e.g. token for Slack).
• DEBUG: (Optional) Enables verbose debug logging when set to "true", "1", or "yes".
• EXTRA_HEADERS: (Optional) Additional HTTP headers in "Header: Value" format (one per line) to attach to outgoing API requests.
• SERVER_URL_OVERRIDE: (Optional) Overrides the base URL from the OpenAPI specification when set, useful for custom deployments.
• TOOL_NAME_MAX_LENGTH: (Optional) Truncates tool names to a max length.
• Additional Variable: OPENAPI_SPEC_URL_<hash> – a variant for unique per-test configurations (falls back to OPENAPI_SPEC_URL).
• IGNORE_SSL_SPEC: (Optional) Set to true to disable SSL certificate verification when fetching the OpenAPI spec.
• IGNORE_SSL_TOOLS: (Optional) Set to true to disable SSL certificate verification for API requests made by tools.

Examples

For testing you can run the uvx command as demonstrated in the examples then interact with the MCP server via JSON-RPC messages to list tools and resources. See the "JSON-RPC Testing" section below.

Glama Example

Glama offers the most minimal configuration for mcp-openapi-proxy requiring only the OPENAPI_SPEC_URL environment variable. This simplicity makes it ideal for quick testing.

1. Verify the OpenAPI Specification

Retrieve the Glama OpenAPI specification:

Ensure the response is a valid OpenAPI JSON document.

2. Configure mcp-openapi-proxy for Glama

Add the following configuration to your MCP ecosystem settings:

3. Testing

Start the service with:

Then refer to the JSON-RPC Testing section for instructions on listing resources and tools.

Fly.io Example

Fly.io provides a simple API for managing machines making it an ideal starting point. Obtain an API token from Fly.io documentation.

1. Verify the OpenAPI Specification

Retrieve the Fly.io OpenAPI specification:

Ensure the response is a valid OpenAPI JSON document.

2. Configure mcp-openapi-proxy for Fly.io

Update your MCP ecosystem configuration:

• OPENAPI_SPEC_URL: Points to the Fly.io OpenAPI specification.
• API_KEY: Your Fly.io API token (replace <your_flyio_token_here>).
• API_AUTH_TYPE: Set to Api-Key for Fly.io’s header-based authentication (overrides default Bearer).

3. Testing

After starting the service refer to the JSON-RPC Testing section for instructions on listing resources and tools.

Render Example

Render offers infrastructure hosting that can be managed via an API. The provided configuration file examples/render-claude_desktop_config.json demonstrates how to set up your MCP ecosystem quickly with minimal settings.

1. Verify the OpenAPI Specification

Retrieve the Render OpenAPI specification:

Ensure the response is a valid OpenAPI document.

2. Configure mcp-openapi-proxy for Render

Add the following configuration to your MCP ecosystem settings:

3. Testing

Launch the proxy with your Render configuration:

Then refer to the JSON-RPC Testing section for instructions on listing resources and tools.

Slack Example

Slack’s API showcases stripping unnecessary token payload using JMESPath. Obtain a bot token from Slack API documentation.

1. Verify the OpenAPI Specification

Retrieve the Slack OpenAPI specification:

Ensure it’s a valid OpenAPI JSON document.

2. Configure mcp-openapi-proxy for Slack

Update your configuration:

• OPENAPI_SPEC_URL: Slack’s OpenAPI spec URL.
• TOOL_WHITELIST: Limits tools to useful endpoint groups (e.g. chat, conversations, users).
• API_KEY: Your Slack bot token (e.g. xoxb-..., replace <your_slack_bot_token>).
• STRIP_PARAM: Removes the token field from the request payload.
• TOOL_NAME_PREFIX: Prepends slack_ to tool names.

3. Testing

After starting the service refer to the JSON-RPC Testing section for instructions on listing resources and tools.

GetZep Example

GetZep offers a free cloud API for memory management with detailed endpoints. Since GetZep did not provide an official OpenAPI specification, this project includes a generated spec hosted on GitHub for convenience. Users can similarly generate OpenAPI specs for any REST API and reference them locally (e.g. file:///path/to/spec.json). Obtain an API key from GetZep's documentation.

1. Verify the OpenAPI Specification

Retrieve the project-provided GetZep OpenAPI specification:

Ensure it’s a valid OpenAPI JSON document. Alternatively, generate your own spec and use a file:// URL to reference a local file.

2. Configure mcp-openapi-proxy for GetZep

Update your configuration:

• OPENAPI_SPEC_URL: Points to the project-provided GetZep Swagger spec (or use file:///path/to/your/spec.json for a local file).
• TOOL_WHITELIST: Limits to /sessions endpoints.
• API_KEY: Your GetZep API key.
• API_AUTH_TYPE: Uses Api-Key for header-based authentication.
• TOOL_NAME_PREFIX: Prepends zep_ to tool names.

3. Testing

After starting the service refer to the JSON-RPC Testing section for instructions on listing resources and tools.

Virustotal Example

This example demonstrates:

• Using a YAML OpenAPI specification file
• Using custom HTTP auth header, "x-apikey"

1. Verify the OpenAPI Specification

Retrieve the Virustotal OpenAPI specification:

Ensure that the response is a valid OpenAPI YAML document.

2. Configure mcp-openapi-proxy for Virustotal

Add the following configuration to your MCP ecosystem settings:

Key configuration points:

• By default, the proxy expects a JSON specification and sends the API key with a Bearer prefix.
• To use a YAML OpenAPI specification, include OPENAPI_SPEC_FORMAT="yaml".
• Note: VirusTotal requires a special authentication header; EXTRA_HEADERS is used to transmit the API key as "x-apikey: ${VIRUSTOTAL_API_KEY}".

3. Testing

Launch the proxy with the Virustotal configuration:

After starting the service, refer to the JSON-RPC Testing section for instructions on listing resources and tools.

Notion Example

Notion’s API requires specifying a particular version via HTTP headers. This example uses the EXTRA_HEADERS environment variable to include the required header, and focuses on verifying the OpenAPI specification.

1. Verify the OpenAPI Specification

Retrieve the Notion OpenAPI specification:

Ensure the response is a valid YAML document.

2. Configure mcp-openapi-proxy for Notion

Add the following configuration to your MCP ecosystem settings:

3. Testing

Launch the proxy with the Notion configuration:

After starting the service, refer to the JSON-RPC Testing section for instructions on listing resources and tools.

Asana Example

Asana provides a rich set of endpoints for managing workspaces, tasks, projects, and users. The integration tests demonstrate usage of endpoints such as GET /workspaces, GET /tasks, and GET /projects.

1. Verify the OpenAPI Specification

Retrieve the Asana OpenAPI specification:

Ensure the response is a valid YAML (or JSON) document.

2. Configure mcp-openapi-proxy for Asana

Add the following configuration to your MCP ecosystem settings:

Note: Most Asana API endpoints require authentication. Set ASANA_API_KEY in your environment or .env file with a valid token.

3. Testing

Start the service with:

You can then use the MCP ecosystem to list and invoke tools for endpoints like /dcim/devices/ and /ipam/ip-addresses/.

APIs.guru Example

APIs.guru provides a directory of OpenAPI definitions for thousands of public APIs. This example shows how to use mcp-openapi-proxy to expose the APIs.guru directory as MCP tools.

1. Verify the OpenAPI Specification

Retrieve the APIs.guru OpenAPI specification:

Ensure the response is a valid OpenAPI YAML document.

2. Configure mcp-openapi-proxy for APIs.guru

Add the following configuration to your MCP ecosystem settings:

3. Testing

Start the service with:

You can then use the MCP ecosystem to list and invoke tools such as listAPIs, getMetrics, and getProviders that are defined in the APIs.guru directory.

NetBox Example

NetBox is an open-source IP address management (IPAM) and data center infrastructure management (DCIM) tool. This example demonstrates how to use mcp-openapi-proxy to expose the NetBox API as MCP tools.

1. Verify the OpenAPI Specification

Retrieve the NetBox OpenAPI specification:

Ensure the response is a valid OpenAPI YAML document.

2. Configure mcp-openapi-proxy for NetBox

Add the following configuration to your MCP ecosystem settings:

Note: Most NetBox API endpoints require authentication. Set NETBOX_API_KEY in your environment or .env file with a valid token.

3. Testing

Start the service with:

You can then use the MCP ecosystem to list and invoke tools for endpoints like /dcim/devices/ and /ipam/ip-addresses/.

Box API Example

You can integrate the Box Platform API using your own developer token for authenticated access to your Box account. This example demonstrates how to expose Box API endpoints as MCP tools.

Example config: examples/box-claude_desktop_config.json

• Set your Box developer token as an environment variable in .env:
  BOX_API_KEY=your_box_developer_token
• Or run the proxy with a one-liner:
  OPENAPI_SPEC_URL="https://raw.githubusercontent.com/APIs-guru/openapi-directory/refs/heads/main/APIs/box.com/2.0.0/openapi.yaml" API_KEY="$BOX_API_KEY" uvx mcp-openapi-proxy

You can now use the MCP ecosystem to list and invoke Box API tools. For integration tests, see tests/integration/test_box_integration.py.

WolframAlpha API Example

You can integrate the WolframAlpha API using your own App ID for authenticated access. This example demonstrates how to expose WolframAlpha API endpoints as MCP tools.

Example config: examples/wolframalpha-claude_desktop_config.json

• Set your WolframAlpha App ID as an environment variable in .env:
  WOLFRAM_LLM_APP_ID=your_wolfram_app_id
• Or run the proxy with a one-liner:
  OPENAPI_SPEC_URL="https://raw.githubusercontent.com/APIs-guru/openapi-directory/refs/heads/main/APIs/wolframalpha.com/v0.1/openapi.yaml" API_KEY="$WOLFRAM_LLM_APP_ID" uvx mcp-openapi-proxy

You can now use the MCP ecosystem to list and invoke WolframAlpha API tools. For integration tests, see tests/integration/test_wolframalpha_integration.py.

Troubleshooting

JSON-RPC Testing

For alternative testing, you can interact with the MCP server via JSON-RPC. After starting the server, paste the following initialization message:

Expected response:

Then paste these follow-up messages:

• Missing OPENAPI_SPEC_URL: Ensure it’s set to a valid OpenAPI JSON URL or local file path.
• Invalid Specification: Verify the OpenAPI document is standard-compliant.
• Tool Filtering Issues: Check TOOL_WHITELIST matches desired endpoints.
• Authentication Errors: Confirm API_KEY and API_AUTH_TYPE are correct.
• Logging: Set DEBUG=true for detailed output to stderr.
• Test Server: Run directly:

License

MIT License