registry = HookRegistry()
    
    # Register a function hook using decorator
    @registry.on(HookEvent.BEFORE_TOOL)
    def validate_tool(event_data):
        if event_data.tool_name == "dangerous":
            return HookResult.deny("Tool is dangerous")
        return HookResult.allow()
    
    # Register a command hook
    registry.register_command(
        event=HookEvent.BEFORE_TOOL,
        command="python /path/to/validator.py",
        matcher="write_*"
    )