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Main Authors: Shi, Xiaoxin, Wan, Jiaxin, Dong, Linkang, Jiang, Wei, Liu, Yue, Huang, Zengfeng
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2603.00030
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author Shi, Xiaoxin
Wan, Jiaxin
Dong, Linkang
Jiang, Wei
Liu, Yue
Huang, Zengfeng
author_facet Shi, Xiaoxin
Wan, Jiaxin
Dong, Linkang
Jiang, Wei
Liu, Yue
Huang, Zengfeng
contents LLM-based function calling enables intelligent agents to interact with external tools and environments, yet autoregressive decoding imposes a fundamental latency bottleneck that limits real-time applications such as embodied intelligence, game AI, and interactive avatars (e.g., 10 Hz control frequency). We observe that function calling differs fundamentally from free-form text generation: structured outputs exhibit substantial token redundancy (delimiters, parameter names), and arguments exhibit weak causal dependencies. Crucially, these two properties must be exploited jointly to achieve real-time performance. We present SimpleTool, which introduces special tokens that serve a dual role: compressing low-entropy tokens (4-6x reduction) while acting as mode selectors that enable independent parallel generation of function name and arguments. This synergistic design achieves 3-6x end-to-end speedup (up to 9.6x) with only +8.2% parallelization overhead. Experiments on five benchmarks across Qwen-series models (0.5B-14B) demonstrate substantial speedup while maintaining competitive or improved accuracy. On Mobile Actions, ST-Qwen-0.5B outperforms Google's FunctionGemma in both accuracy and latency consistency. With quantization on consumer-grade GPU, SimpleTool achieves 61.2ms P50 latency, enabling 16 Hz real-time control at 4B model scale, bridging the gap between LLM function calling and latency-critical real-world deployment.
format Preprint
id arxiv_https___arxiv_org_abs_2603_00030
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle SimpleTool: Parallel Decoding for Real-Time LLM Function Calling
Shi, Xiaoxin
Wan, Jiaxin
Dong, Linkang
Jiang, Wei
Liu, Yue
Huang, Zengfeng
Computation and Language
LLM-based function calling enables intelligent agents to interact with external tools and environments, yet autoregressive decoding imposes a fundamental latency bottleneck that limits real-time applications such as embodied intelligence, game AI, and interactive avatars (e.g., 10 Hz control frequency). We observe that function calling differs fundamentally from free-form text generation: structured outputs exhibit substantial token redundancy (delimiters, parameter names), and arguments exhibit weak causal dependencies. Crucially, these two properties must be exploited jointly to achieve real-time performance. We present SimpleTool, which introduces special tokens that serve a dual role: compressing low-entropy tokens (4-6x reduction) while acting as mode selectors that enable independent parallel generation of function name and arguments. This synergistic design achieves 3-6x end-to-end speedup (up to 9.6x) with only +8.2% parallelization overhead. Experiments on five benchmarks across Qwen-series models (0.5B-14B) demonstrate substantial speedup while maintaining competitive or improved accuracy. On Mobile Actions, ST-Qwen-0.5B outperforms Google's FunctionGemma in both accuracy and latency consistency. With quantization on consumer-grade GPU, SimpleTool achieves 61.2ms P50 latency, enabling 16 Hz real-time control at 4B model scale, bridging the gap between LLM function calling and latency-critical real-world deployment.
title SimpleTool: Parallel Decoding for Real-Time LLM Function Calling
topic Computation and Language
url https://arxiv.org/abs/2603.00030