SkillReducer: Optimizing LLM Agent Skills for Token Efficiency
arXiv:2603.29919v1 Announce Type: new Abstract: LLM-based coding agents rely on \emph{skills}, pre-packaged instruction sets that extend agent capabilities, yet every token of skill content injected into the context window incurs both monetary cost and attention dilution. To understand the severity of this problem, we conduct a large-scale empirical study of 55,315 publicly available skills and find systemic inefficiencies: 26.4\% lack routing descriptions entirely, over 60\% of body content is non-actionable, and reference files can inject tens of thousands of tokens per invocation. Motivated by these findings, we present \textsc{SkillReducer}, a two-stage optimization framework. Stage~1 optimizes the routing layer by compressing verbose descriptions and generating missing ones via advers
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Abstract:LLM-based coding agents rely on \emph{skills}, pre-packaged instruction sets that extend agent capabilities, yet every token of skill content injected into the context window incurs both monetary cost and attention dilution. To understand the severity of this problem, we conduct a large-scale empirical study of 55,315 publicly available skills and find systemic inefficiencies: 26.4% lack routing descriptions entirely, over 60% of body content is non-actionable, and reference files can inject tens of thousands of tokens per invocation. Motivated by these findings, we present \textsc{SkillReducer}, a two-stage optimization framework. Stage
1 optimizes the routing layer by compressing verbose descriptions and generating missing ones via adversarial delta debugging. Stage2 restructures skill bodies through taxonomy-driven classification and progressive disclosure, separating actionable core rules from supplementary content loaded on demand, validated by faithfulness checks and a self-correcting feedback loop. Evaluated on 600 skills and the SkillsBench benchmark, \textsc{SkillReducer} achieves 48% description compression and 39% body compression while improving functional quality by 2.8%, revealing a \emph{less-is-more} effect where removing non-essential content reduces distraction in the context window. These benefits transfer across five models from four families with a mean retention of 0.965, and generalize to an independent agent framework.
Subjects:
Software Engineering (cs.SE)
Cite as: arXiv:2603.29919 [cs.SE]
(or arXiv:2603.29919v1 [cs.SE] for this version)
https://doi.org/10.48550/arXiv.2603.29919
arXiv-issued DOI via DataCite (pending registration)
Submission history
From: Zongjie Li [view email] [v1] Tue, 31 Mar 2026 15:57:53 UTC (997 KB)
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