ZERA: Zero-prompt Evolving Refinement Agent – From Zero Instructions to Structured Prompts via Principle-based Optimization

ACL ARR 2025 May Submission3423 Authors

Abstract: Automatic Prompt Optimization (APO) improves large language model (LLM) performance by refining prompts for specific tasks. However, prior APO methods typically focus only on user prompts, rely on unstructured feedback, and require large sample sizes and long iteration cycles—making them costly and brittle. We propose ZERA (Zero-prompt Evolving Refinement Agent), a novel framework that jointly optimizes both system and user prompts through principled, low-overhead refinement. ZERA scores prompts using eight generalizable criteria with automatically inferred weights, and revises prompts based on these structured critiques. This enables fast convergence to high-quality prompts using minimal examples and short iteration cycles. We evaluate ZERA across five LLMs and nine diverse datasets spanning reasoning, summarization, and code generation tasks. Experimental results demonstrate consistent improvements over strong baselines. Further ablation studies highlight the contribution of each component to more effective prompt construction. Our implementation including all prompts will be publicly available.

Paper Type: Long

Research Area: Interpretability and Analysis of Models for NLP

Research Area Keywords: Generation, Interpretability and Analysis of Models for NLP, Machine Learning for NLP

Contribution Types: Model analysis & interpretability

Languages Studied: English

Keywords: LLM, Document Processing, Domain Generalization

Submission Number: 3423