Do Multimodal Agents Really Benefit from Tool Use? A Systematic Study of Capability Gains

Fuente: arXiv
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Autores principales: Guo, Garvin, Yu, Donglei, Chen, Yu, Wang, Xiang, Li, Shuai, Zhao, Xinpei, Liu, Huaxing, Wang, Qinghao, Liao, Minpeng
Formato: Preprint
Publicado: 2026
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author Guo, Garvin
Yu, Donglei
Chen, Yu
Wang, Xiang
Li, Shuai
Zhao, Xinpei
Liu, Huaxing
Wang, Qinghao
Liao, Minpeng
author_facet Guo, Garvin
Yu, Donglei
Chen, Yu
Wang, Xiang
Li, Shuai
Zhao, Xinpei
Liu, Huaxing
Wang, Qinghao
Liao, Minpeng
contents Tool-augmented multimodal agents show strong benchmark gains, often taken as evidence that agents have learned to use tools. We argue that this interpretation can be premature: a tool-call trace alone does not show whether the tool supplied answer-critical information. We study two representative ``thinking with images'' agents, Thyme and DeepEyesV2, across real-world understanding, OCR, chart understanding, and mathematical reasoning. Each agent is compared with its Tool-Free counterpart and with a Pure-Text Reasoner trained from the same source pool without tool-calling trajectories. Tool access yields little consistent aggregate improvement, does not reliably reduce generated-token cost, and leaves only a small tool-only solved set: 93% of DeepEyesV2's tool-solved problems and 96% of Thyme's are also solved by at least one non-tool setting. Mechanism ablations further show that the full tool-use loop does not consistently outperform either the tool-call format or the returned execution result alone. In the settings we study, the analyzed agents appear to learn tool-calling patterns more reliably than tool-contributed capabilities, suggesting that evaluation should distinguish tool availability from whether tools actually expand what agents can solve.
format Preprint
id arxiv_https___arxiv_org_abs_2606_02357
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Do Multimodal Agents Really Benefit from Tool Use? A Systematic Study of Capability Gains
Guo, Garvin
Yu, Donglei
Chen, Yu
Wang, Xiang
Li, Shuai
Zhao, Xinpei
Liu, Huaxing
Wang, Qinghao
Liao, Minpeng
Computer Vision and Pattern Recognition
Artificial Intelligence
Tool-augmented multimodal agents show strong benchmark gains, often taken as evidence that agents have learned to use tools. We argue that this interpretation can be premature: a tool-call trace alone does not show whether the tool supplied answer-critical information. We study two representative ``thinking with images'' agents, Thyme and DeepEyesV2, across real-world understanding, OCR, chart understanding, and mathematical reasoning. Each agent is compared with its Tool-Free counterpart and with a Pure-Text Reasoner trained from the same source pool without tool-calling trajectories. Tool access yields little consistent aggregate improvement, does not reliably reduce generated-token cost, and leaves only a small tool-only solved set: 93% of DeepEyesV2's tool-solved problems and 96% of Thyme's are also solved by at least one non-tool setting. Mechanism ablations further show that the full tool-use loop does not consistently outperform either the tool-call format or the returned execution result alone. In the settings we study, the analyzed agents appear to learn tool-calling patterns more reliably than tool-contributed capabilities, suggesting that evaluation should distinguish tool availability from whether tools actually expand what agents can solve.
title Do Multimodal Agents Really Benefit from Tool Use? A Systematic Study of Capability Gains
topic Computer Vision and Pattern Recognition
Artificial Intelligence
url https://arxiv.org/abs/2606.02357