The Art of Tool Interface Design

Yunnan Wu, Qile P. Chen, Deshank Baranwal, Jinlong Zhou, Jian Yuan


Abstract
We present an agentic framework, Thinker, which achieves state of art performance in challenging reasoning tasks for realistic customer service scenarios that involve complex business logic and human interactions via long horizons. On the 𝜏-bench retail dataset, Thinker achieves 82.6% success rate with GPT-4o (version 2024-06-01) (baseline: 68.3%), and 81.9% success rate with Llama-3.1 405B (baseline: 49.6%), without any fine-tuning. Thinker effectively closes the gap in reasoning capabilities between the base models by introducing proper structure.The key features of the Thinker framework are: (1) State-Machine Augmented Generation (SMAG), which represents business logic as state machines and the LLM uses state machines as tools. (2) Delegation of tasks from the main reasoning loop to LLM-powered tools.(3) Adaptive context management.Our prompting-only solution achieves signficant gains, while still maintaining a simple and standard agentic architecture with a ReAct style reasoning loop. The key is to innovate on the tool interface design, as exemplified by SMAG and the LLM-powered tools.
Anthology ID:
2025.realm-1.5
Volume:
Proceedings of the 1st Workshop for Research on Agent Language Models (REALM 2025)
Month:
July
Year:
2025
Address:
Vienna, Austria
Editors:
Ehsan Kamalloo, Nicolas Gontier, Xing Han Lu, Nouha Dziri, Shikhar Murty, Alexandre Lacoste
Venues:
REALM | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
63–79
Language:
URL:
https://preview.aclanthology.org/mtsummit-25-ingestion/2025.realm-1.5/
DOI:
10.18653/v1/2025.realm-1.5
Bibkey:
Cite (ACL):
Yunnan Wu, Qile P. Chen, Deshank Baranwal, Jinlong Zhou, and Jian Yuan. 2025. The Art of Tool Interface Design. In Proceedings of the 1st Workshop for Research on Agent Language Models (REALM 2025), pages 63–79, Vienna, Austria. Association for Computational Linguistics.
Cite (Informal):
The Art of Tool Interface Design (Wu et al., REALM 2025)
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PDF:
https://preview.aclanthology.org/mtsummit-25-ingestion/2025.realm-1.5.pdf