@inproceedings{jiang-etal-2026-emtir,
    title = "{EMTIR}-{GRPO}: Efficient Multi-Tool Augmented Large Language Models via Reinforcement Learning",
    author = "Jiang, Shixin  and
      Zhu, Zhihao  and
      Liang, Jiafeng  and
      Wu, Yang  and
      Liu, Ming  and
      Qin, Bing",
    editor = "Liakata, Maria  and
      Moreira, Viviane P.  and
      Zhang, Jiajun  and
      Jurgens, David",
    booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {ACL} 2026",
    month = jul,
    year = "2026",
    address = "San Diego, California, United States",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/ingest-acl/2026.findings-acl.1388/",
    pages = "27877--27894",
    ISBN = "979-8-89176-395-1",
    abstract = "Tool-integrated reasoning (TIR) enables large language models (LLMs) to invoke external tools for tasks beyond their internal capacity but often suffers from tool overuse.Existing approaches leverage imitation learning or reward shaping to improve efficiency, yet mainly target single-tool scenarios and ignore the varying invocation costs across tools in multi-tool reasoning (MTIR). To address these gaps, we propose EMTIR-GRPO, a simple yet effective RL algorithm for cost-aware MTIR. Built upon GRPO, we introduce a composite reward considering format completeness, answer correctness, and tool efficiency.By incorporating a cost-aware coefficient with group optimal cost estimation, EMTIR-GRPO explicitly models heterogeneous tool costs and encourages more cost-effective tool-use strategies. Experiments on MTIR-QA and MTIR-TC demonstrate significant efficiency gains (e.g., $\Delta$+10.9 on Tool-Star-7B and $\Delta$+3.6 on ReCall-7B) while maintaining or even improving accuracy (e.g., 55.4 vs. 52.0 on Tool-Star-7B). Additional budget-constrained and tool-free evaluations further validate its effectiveness in maximizing cost-efficiency and reducing cognitive offloading."
}