01 · Observe, decide, act

def search_hotels(city):
    return [("Hana Inn", 12000), ("Kamo Stay", 15500)]

def convert(amount, frm, to):
    return round(amount * 0.0065)  # example JPY to USD rate

TOOLS = {"search_hotels": search_hotels, "convert": convert}

def fake_model(history):  # stands in for the API call
    results = [m["content"] for m in history if m["role"] == "tool"]
    if not results:
        return {"tool": "search_hotels", "input": {"city": "Kyoto"}}
    if len(results) == 1:
        nightly = min(price for _, price in results[0])
        return {"tool": "convert",
                "input": {"amount": 3 * nightly, "frm": "JPY", "to": "USD"}}
    return {"answer": f"About ${results[1]} for 3 nights."}

history = [{"role": "user", "content": "3 nights, cheapest hotel in Kyoto, in USD?"}]
for step in range(1, 9):  # the step limit
    reply = fake_model(history)
    if "answer" in reply:
        print("final:", reply["answer"])
        break
    result = TOOLS[reply["tool"]](**reply["input"])
    print(f"step {step}: {reply['tool']} -> {result}")
    history += [{"role": "assistant", "content": reply},
                {"role": "tool", "content": result}]
else:
    print("stopped at the step limit")
print(len(history), "messages")
# step 1: search_hotels -> [('Hana Inn', 12000), ('Kamo Stay', 15500)]
# step 2: convert -> 234
# final: About $234 for 3 nights.
# 5 messages

The else on the for runs only if the loop uses up its steps without an answer. Swap fake_model for a real API call and the loop stays the same: the model decides the moves by reading the same history.