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.

Overview

The package offers two operational modes:

Low-Level Mode (Default): Dynamically registers tools corresponding to all API endpoints specified in an OpenAPI document (e.g., /chat/completions becomes chat_completions()).
FastMCP Mode (Simple Mode): Provides a streamlined approach, exposing a predefined set of tools (e.g., list_functions() and call_functions()) 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.
MCP Integration: Seamlessly integrates with MCP ecosystems for invoking REST APIs as tools.

Installation

Install the package directly from PyPI using the following command:

uvx mcp-openapi-proxy

MCP Ecosystem Integration

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

{
    "mcpServers": {
        "mcp-openapi-proxy": {
            "command": "uvx",
            "args": ["mcp-openapi-proxy"],
            "env": {
                "OPENAPI_SPEC_URL": "${OPENAPI_SPEC_URL}",
                "API_KEY": "",
                "TOOL_WHITELIST": "",
                "TOOL_NAME_PREFIX": ""
            }
        }
    }
}

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.
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.

Examples

This section will expand incrementally with new examples added periodically. Each example demonstrates how to configure mcp-openapi-proxy for a specific API, starting with GetZep, which leverages a free cloud API accessible with a GetZep API key.

GetZep Example

GetZep provides a free cloud API for memory management, making it an excellent starting point for testing. Obtain an API key from GetZep's documentation.

1. Verify the OpenAPI Specification

Retrieve the GetZep OpenAPI specification:

curl https://raw.githubusercontent.com/matthewhand/mcp-openapi-proxy/refs/heads/main/examples/getzep.swagger.json

Ensure the response is a valid OpenAPI JSON document.

2. Configure mcp-openapi-proxy for GetZep

Update your MCP ecosystem configuration as follows:

{
    "mcpServers": {
        "getzep": {
            "command": "uvx",
            "args": ["mcp-openapi-proxy"],
            "env": {
                "OPENAPI_SPEC_URL": "https://raw.githubusercontent.com/matthewhand/mcp-openapi-proxy/refs/heads/main/examples/getzep.swagger.json",
                "TOOL_WHITELIST": "/sessions,/sessions/{sessionId},/sessions-ordered,/sessions/{sessionId}/memory,/sessions/{sessionId}/messages",
                "API_KEY": "<your_getzep_api_key>",
                "API_AUTH_TYPE": "Api-Key",
                "SERVER_URL_OVERRIDE": "https://api.getzep.com",
                "TOOL_NAME_PREFIX": "getzep"
            }
        }
    }
}

OPENAPI_SPEC_URL: Points to the GetZep Swagger specification.
TOOL_WHITELIST: Limits tools to specific endpoints (e.g., /sessions, /sessions/{sessionId}/memory).
API_KEY: Your GetZep API key (replace <your_getzep_api_key>).
API_AUTH_TYPE: Specifies Api-Key for GetZep’s authentication.
SERVER_URL_OVERRIDE: Sets the base URL to GetZep’s API.
TOOL_NAME_PREFIX: Prepends getzep to tool names (e.g., getzep_sessions).

3. Resulting Tools

This configuration generates tools such as:

[
    {"name": "getzep_sessions", "description": "List all sessions"},
    {"name": "getzep_sessions_sessionid", "description": "Get a specific session by ID"},
    {"name": "getzep_sessions_ordered", "description": "List sessions in order"},
    {"name": "getzep_sessions_sessionid_memory", "description": "Retrieve memory for a session"},
    {"name": "getzep_sessions_sessionid_messages", "description": "Get messages for a session"}
]

4. Testing

Run the server with uvx to verify:

OPENAPI_SPEC_URL="https://raw.githubusercontent.com/matthewhand/mcp-openapi-proxy/refs/heads/main/examples/getzep.swagger.json" API_KEY="<your_getzep_api_key>" uvx mcp-openapi-proxy

Additional examples (e.g., OpenWebUI, Fly.io) will be added incrementally to this section over time.

Troubleshooting

Missing OPENAPI_SPEC_URL: Ensure the environment variable is set to a valid OpenAPI JSON URL.
Invalid Specification: Confirm the OpenAPI document adheres to the standard.
Tool Filtering Issues: Verify TOOL_WHITELIST correctly specifies desired endpoints.
Logging: Check logs at OPENAPI_LOGFILE_PATH (if set) for diagnostic details.
Installation Verification: Test the server directly:

uvx mcp-openapi-proxy

License

This project is licensed under the MIT License. See the LICENSE file for details.

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