MCP Tool Transform Proxy

A Python CLI that proxies remote MCP servers while applying configurable tool transformations (name, description, arguments). Sits transparently between MCP clients (like Claude Desktop) and remote MCP servers.

Installation

pip install mcp-transform-proxy

Quick Start

1. Create a configuration file:

{
  "mcpServers": {
    "myserver": {
      "url": "https://my-mcp-server.example.com/mcp",
      "tools": {
        "original_tool": {
          "description": "Enhanced description with context about when to use this tool"
        }
      }
    }
  }
}

2. Run the proxy:

mcp-transform-proxy --config config.json

Configuration

Full Configuration Example

{
  "proxy": {
    "name": "MyToolProxy",
    "transport": "stdio",
    "port": 8080
  },
  "mcpServers": {
    "weather": {
      "url": "https://weather-api.example.com/mcp",
      "transport": "sse",
      "tools": {
        "get_weather": {
          "name": "check_weather",
          "description": "Check current weather. Use when user asks about weather.",
          "arguments": {
            "units": {
              "default": "metric",
              "hide": true
            },
            "location": {
              "name": "city",
              "description": "City name to check"
            }
          }
        },
        "internal_tool": {
          "enabled": false
        }
      }
    }
  }
}

Configuration Reference

Proxy Settings

Field	Type	Default	Description
name	string	"MCP Transform Proxy"	Name of the proxy server
transport	"stdio" | "http"	"stdio"	Transport mode
port	integer	8080	HTTP port (only used with http transport)

Server Settings

Field	Type	Required	Description
url	string	Yes	URL of the upstream MCP server
transport	"streamable-http" | "sse"	No	Transport for upstream connection
tools	object	No	Tool transformations (keyed by tool name)

Tool Transformations

Field	Type	Default	Description
name	string	null	Rename the tool
description	string	null	Replace tool description
enabled	boolean	true	Set to false to hide the tool
arguments	object	{}	Argument transformations

Argument Transformations

Field	Type	Default	Description
name	string	null	Rename the argument
description	string	null	Replace argument description
default	any	null	Set a default value
hide	boolean	false	Hide argument from clients

Tool Name Prefixing

FastMCP's composite proxy automatically prefixes tool names with the server name. For example, if you have a server named weather with a tool get_forecast, the prefixed name will be weather_get_forecast.

When configuring tool transforms, use the original tool name (without prefix) in your config - the proxy handles prefixing internally.

CLI Options

Usage: mcp-transform-proxy [OPTIONS]

Options:
  -c, --config PATH      Path to JSON config file (required)
  -t, --transport TEXT   Override transport mode (stdio or http)
  -p, --port INTEGER     Override HTTP port
  --version              Show version
  --help                 Show this message and exit

Development

# Clone the repository
git clone https://github.com/bbrowning/mcp-transform-proxy.git
cd mcp-transform-proxy

# Create virtual environment
python -m venv .venv
source .venv/bin/activate

# Install in development mode
pip install -e ".[dev]"

# Run tests
pytest

# Run linter
ruff check .

# Run type checker
mypy src

License

MIT