增加工具使用功能

tests/test_api.py

@@ -136,7 +136,9 @@ def test_multi_turn_request_contains_full_history(
         "completion_tokens": 2,
         "total_tokens": 12,
     }
+    assert second.json()["tools_use"] == []
     datetime.fromisoformat(second.json()["message"]["created_at"])
+    assert "tool_calls" not in second.json()["message"]
     data = json.loads((tmp_path / f"{session_id}.json").read_text())
     assert [message["content"] for message in data["messages"]] == [
         "first",