Tool Use (Function Calling)

Tools let Claude call your Python functions. The model decides when to call a tool and what arguments to pass — you execute it and feed the result back.

The loop:

1. Send message with tool definitions
2. If stop_reason == "tool_use", execute the requested tools
3. Append the assistant turn + tool results and call again
4. Repeat until stop_reason == "end_turn"

Why care? This is how AI goes from chatbot to agent. Claude can look up live data, call external APIs, or run calculations mid-conversation — all while you stay in control of execution.

Task

Complete answer_with_tools(question, client). A get_exchange_rate function and its tool schema are already defined. Run the agentic loop until the model returns a final text answer.