User: 'Book a flight to London next Tuesday'
1. LLM analyzes request
2. LLM outputs: search_flights('London', '2026-05-19')
3. Your code executes the function
4. Results returned to LLM
5. LLM generates natural language response

tool = {
    'type': 'function',
    'function': {
        'name': 'search_hotels',
        'description': 'Find hotels in a city',
        'parameters': {
            'type': 'object',
            'properties': {
                'city': {'type': 'string'},
                'check_in': {'type': 'string'},
                'max_price': {'type': 'number'}
            },
            'required': ['city', 'check_in']
        }
    }
}

User Prompt -> LLM generates -> tool_calls? -> Yes: Parse -> Execute -> Return -> LLM
                                                            |
                                                     No: Return response