# Hello World UV Runtime Example (Experimental)

> **Note:** UV runtime support is experimental and may change in future versions.

This example demonstrates a minimal MCP server using **UV runtime**.

## What is UV Runtime?

UV runtime lets Claude Desktop automatically manage Python and dependencies for your extension:
- Downloads the correct Python version for the user's platform
- Creates an isolated virtual environment
- Installs dependencies from `pyproject.toml`
- Works cross-platform (Windows, macOS, Linux) without user setup

## Structure

```
hello-world-uv/
├── manifest.json       # server.type = "uv"
├── pyproject.toml      # Dependencies listed here
├── .mcpbignore        # Exclude build artifacts
└── src/
    └── server.py       # MCP server implementation
```

## Key Differences from Python Runtime

**UV Runtime** (this example):
- `server.type = "uv"`
- No bundled dependencies
- No `mcp_config` needed
- Small bundle size (~2 KB)
- Works on any platform

**Python Runtime** (traditional):
- `server.type = "python"`
- Must bundle dependencies in `server/lib/`
- Requires `mcp_config` with PYTHONPATH
- Larger bundle size
- Only works with pure Python (no compiled deps)

## Installing

```bash
mcpb pack
```

Install the generated `.mcpb` file in Claude Desktop.

## Testing Locally

```bash
# Install dependencies
uv sync

# Run server
uv run src/server.py
```

## Tools

- **say_hello** - Greets a person by name