# MCP Server Framework

A general-purpose Model Context Protocol (MCP) server that provides tools for Claude Code and Claude Desktop.

## Quick Start

```bash
# Install dependencies
cd mcp-server
pip install -r requirements.txt

# Test the server runs (Ctrl+C to stop)
PYTHONPATH=src python -m mcp_server.server
```

## Project Structure

```
mcp-server/
├── src/mcp_server/
│   ├── server.py          # Main FastMCP server
│   ├── config.py          # Environment-based configuration
│   └── tools/
│       ├── __init__.py    # Tool registry
│       ├── echo_tool.py   # Example: basic echo tools
│       ├── datetime_tool.py  # Example: date/time utilities
│       └── file_tool.py   # Example: file operations
├── configs/               # Client configuration templates
└── requirements.txt
```

## Configuration

The server is configured via environment variables:

| Variable | Description | Default |
|----------|-------------|---------|
| `MCP_SERVER_NAME` | Display name for the server | `mcp-server` |
| `MCP_LOG_LEVEL` | Logging level (DEBUG, INFO, WARNING, ERROR) | `INFO` |
| `MCP_ALLOWED_PATHS` | Comma-separated paths for file tools | (none) |
| `MCP_CUSTOM_VAR_*` | Custom variables accessible via config | (none) |

## Included Tools

### Echo Tools
- `echo` - Echo back a message
- `echo_uppercase` - Echo in uppercase
- `echo_reverse` - Echo reversed

### DateTime Tools
- `get_current_time` - Get current UTC time
- `get_timestamp` - Get current Unix timestamp
- `parse_timestamp` - Convert timestamp to readable format
- `time_difference` - Calculate time between two timestamps

### File Tools (requires `MCP_ALLOWED_PATHS`)
- `list_directory` - List directory contents
- `read_file` - Read file contents
- `get_file_info` - Get file/directory metadata
- `get_allowed_paths` - Show configured allowed paths

## Setting Up Clients

### Claude Desktop

1. Open `~/Library/Application Support/Claude/claude_desktop_config.json` (macOS)
2. Add your server configuration:

```json
{
  "mcpServers": {
    "my-mcp-server": {
      "command": "python",
      "args": ["-m", "mcp_server.server"],
      "cwd": "/full/path/to/mcp-server",
      "env": {
        "PYTHONPATH": "/full/path/to/mcp-server/src",
        "MCP_ALLOWED_PATHS": "/Users/you/Documents"
      }
    }
  }
}
```

3. Restart Claude Desktop completely (Cmd+Q, then relaunch)

### Claude Code

Create `.mcp.json` in your project root:

```json
{
  "mcpServers": {
    "my-mcp-server": {
      "command": "python",
      "args": ["-m", "mcp_server.server"],
      "cwd": "${workspaceFolder}/mcp-server",
      "env": {
        "PYTHONPATH": "${workspaceFolder}/mcp-server/src",
        "MCP_ALLOWED_PATHS": "${workspaceFolder}"
      }
    }
  }
}
```

## Adding New Tools

1. Create a new file in `src/mcp_server/tools/`:

```python
# src/mcp_server/tools/my_tool.py
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from mcp.server.fastmcp import FastMCP
    from ..config import ServerConfig


def register(mcp: "FastMCP", config: "ServerConfig") -> None:
    """Register my tools with the server."""

    @mcp.tool()
    def my_function(param: str, count: int = 1) -> str:
        """
        Description shown to Claude.

        Args:
            param: What this parameter does
            count: Optional count with default

        Returns:
            What the tool returns
        """
        return f"Result: {param} x {count}"
```

2. Register it in `src/mcp_server/tools/__init__.py`:

```python
def register_all_tools(mcp: "FastMCP", config: "ServerConfig") -> None:
    from . import echo_tool, datetime_tool, file_tool, my_tool  # Add import

    echo_tool.register(mcp, config)
    datetime_tool.register(mcp, config)
    file_tool.register(mcp, config)
    my_tool.register(mcp, config)  # Add registration
```

3. Restart Claude Desktop/Code to pick up the new tool.

## Tool Design Guidelines

1. **Clear docstrings**: The description and parameter docs are sent to Claude
2. **Type hints**: All parameters and returns need type hints (defines the JSON schema)
3. **Return strings**: Tools should return string results for best compatibility
4. **Error handling**: Return user-friendly error messages rather than raising exceptions
5. **Use config**: Access `config` for environment-specific settings (like allowed paths)

## Troubleshooting

**Server won't start:**
- Ensure `PYTHONPATH` includes the `src` directory
- Check that `mcp` package is installed: `pip install mcp[cli]`

**Tools not appearing in Claude:**
- Verify the config JSON is valid
- Check the `cwd` path is correct
- Restart Claude Desktop completely (Cmd+Q on Mac)

**File tools return "not in allowed directories":**
- Set `MCP_ALLOWED_PATHS` to comma-separated directory paths
- Paths must be absolute

## Dependencies

- Python 3.10+
- `mcp[cli]>=1.0.0`