MCP Dynamic Tools

Drop Python files, get MCP tools instantly.

A dynamic MCP server that automatically discovers Python files in a directory and exposes them as tools to any MCP-compatible AI client. Created through collaboration between Ben Wilson and Claude (Anthropic).

How it works

# 1. Write a Python file or have the LLM write one
def invoke(arguments):
    """Generate a secure password
    
    Parameters:
    - length: Length of password (default: 12)
    - include_symbols: Include special characters (default: true)
    """
    import random, string
    length = int(arguments.get('length', 12))
    chars = string.ascii_letters + string.digits
    if arguments.get('include_symbols', 'true').lower() == 'true':
        chars += "!@#$%^&*"
    return ''.join(random.choice(chars) for _ in range(length))

# 2. Save it to your tools directory
echo "# Above code" > tools/password_generator.py

# 3. AI can now use it immediately (after restart in Claude Desktop)
🤖 "Generate a 16-character password with symbols"
🔧 Tool: password_generator(length="16", include_symbols="true")
📤 Result: "K9#mP2$vR8@nQ3!x"

Quick Start

1. Clone and Setup

git clone https://github.com/your-username/mcp-dynamic-tools
cd mcp-dynamic-tools

2. Create Tools Directory

mkdir tools

3. Configure Your MCP Client

Claude Desktop (~/.config/claude_desktop_config.json):

{
  "mcpServers": {
    "mcp-dynamic-tools": {
      "command": "python3",
      "args": [
        "/path/to/mcp-dynamic-tools/src/mcp_dynamic_tools/server.py",
        "--tools-dir",
        "/path/to/tools"
      ]
    }
  }
}

4. Create Your First Tool

# tools/hello.py
def invoke(arguments):
    """Say hello to someone
    
    Parameters:
    - name: The person to greet
    """
    name = arguments.get('name', 'World')
    return f"Hello, {name}! 👋"

5. Restart Your MCP Client

Your hello tool is now available to any AI using your MCP client!

How It Works

File Discovery: Server monitors your tools directory
Code Analysis: Validates Python files have invoke(arguments) function
Schema Extraction: Parses docstrings for parameter definitions
MCP Integration: Exposes tools via standard MCP protocol
Error Handling: Provides detailed feedback for debugging

Writing Tools

Function Signature

Every tool must have this exact signature:

def invoke(arguments):
    # Your tool logic here
    return result

Documentation Format

def invoke(arguments):
    """Brief description of what the tool does
    
    Parameters:
    - param_name: Description of the parameter
    - another_param: Description with (default: value)
    """

Example Tools

Text Processor:

def invoke(arguments):
    """Transform text in various ways
    
    Parameters:
    - text: The text to transform
    - operation: Type of transformation (uppercase, lowercase, reverse)
    """
    text = arguments.get('text', '')
    operation = arguments.get('operation', 'uppercase')
    
    if operation == 'uppercase':
        return text.upper()
    elif operation == 'lowercase':
        return text.lower()
    elif operation == 'reverse':
        return text[::-1]
    else:
        return f"Unknown operation: {operation}"

API Caller:

def invoke(arguments):
    """Fetch data from a REST API
    
    Parameters:
    - url: The API endpoint to call
    - method: HTTP method (default: GET)
    """
    import urllib.request
    import json
    
    url = arguments.get('url')
    method = arguments.get('method', 'GET')
    
    if not url:
        return "Error: URL is required"
    
    try:
        with urllib.request.urlopen(url) as response:
            return json.loads(response.read())
    except Exception as e:
        return f"Error: {str(e)}"

Robust Error Handling

The server provides detailed error messages to help you debug:

Syntax Errors: Shows line numbers and specific issues
Import Errors: Reports missing dependencies
Function Signature: Validates invoke(arguments) signature
Runtime Errors: Captures and reports execution problems

Known Limitations

Claude Desktop 0.9.2

Claude Desktop currently doesn't support dynamic tool discovery (see discussion). This means:

✅ Tools work perfectly once discovered
❌ Restart required when adding new tools
🔄 Future support planned - our server is ready with listChanged: true

Workaround: Restart Claude Desktop after adding new tools.

Tool Naming in Claude Desktop

Tools appear with server prefix: local__mcp-dynamic-tools__your_tool_name

Contributing

This project was created through human-AI collaboration. We welcome contributions!

Fork the repository
Create your feature branch
Add tests for new functionality
Submit a pull request

License

MIT License - see LICENSE file for details.

Acknowledgments

Ben Vierck - Architecture and development
Claude (Anthropic) - Co-development and testing
MCP Community - Protocol development and feedback