ToolFuse: Documentation-Intent Fusion for Training-Free Tool Retrieval

Shao-Cheng Lu, Shui-Hsiang Hsu, Chen-Jui Yu, Yao-Chung Fan


Abstract
Tool retrieval is a necessary first step for tool-augmented LLMs once the set of available tools grows to thousands or more, and itscentral difficulty stems from two gaps. A user query states what the user wants to accomplish in task-centric language, whereas tooldocumentation describes functionality, parameters, and calling conditions in function-centric terms. This low lexical overlap produces aQuery-Documentation Mismatch. Complex queries also bundle several functional needs at once, while a single tool usually covers only one,producing a Multi-Intent Query Mismatch. We present ToolFuse, a training-free framework that addresses each gap on a different side ofretrieval. On the tool side, Complementarity-based Semantic Fusion treats tool documentation and LLM-generated synthetic intent as adocumentation view and an intent view of the same tool, encodes them separately, and assigns each tool a fusion weight from the geometriccomplementarity between its two views in vector space, without fine-tuning the frozen dense encoder. On the query side, QueryDecomposition splits a multi-intent query into focused sub-queries, retrieves for each, and aggregates the results with rank-aware round-robin. On ToolBench, the full ToolFuse raises the Per-Split average NDCG@5 of Qwen3-Embedding-0.6B from 64.72 to 75.49, with consistentgains across three additional dense encoder backbones.
Anthology ID:
2026.realm-1.99
Volume:
Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026)
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Ehsan Kamalloo, Nicolas Gontier, Nikolai Rozanov, Maryam Hashemzadeh, Akhil Arora
Venues:
REALM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1420–1443
Language:
URL:
https://aclanthology.org/2026.realm-1.99/
DOI:
Bibkey:
Cite (ACL):
Shao-Cheng Lu, Shui-Hsiang Hsu, Chen-Jui Yu, and Yao-Chung Fan. 2026. ToolFuse: Documentation-Intent Fusion for Training-Free Tool Retrieval. In Proceedings of the Second Workshop for REsearch on Agent Language Models (REALM 2026), pages 1420–1443, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
ToolFuse: Documentation-Intent Fusion for Training-Free Tool Retrieval (Lu et al., REALM 2026)
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PDF:
https://aclanthology.org/2026.realm-1.99.pdf