ReTool: Reinforcement Learning for Strategic Tool Use in LLMs - Feng, Jiazhan; Huang, Shijue; Qu, Xingwei; Zhang, Ge; Qin, Yujia; Zhong, Baoquan; Jiang, Chengquan; Chi, Jinxin; Zhong, Wanjun (International Conference on Learning Representations, 2026)