E-commerce stores increasingly use Large Language Models (LLMs) to enhance catalog data quality through automated regeneration. A critical challenge is accurately predicting missing structured attribute values across multilingual product catalogs, where LLM performance varies significantly by language. While existing approaches leverage general knowledge through prompt engineering and external retrieval, more effective and accurate signals for attribute prediction can exist within the catalog ecosystem itself-similar products often share consistent patterns and structural relationships, and may have the missing attributes filled. Therefore, this paper introduces PatternRAG, a novel retrieval-augmented system that strategically leverages existing product catalog entries to guide LLM predictions for missing attributes. Our approach introduces a multi-stage retrieval framework that progressively refines the search space based on product type, uses textual similarity, glance views and brand relationships to identify the most relevant attribute-filled examples for LLM prediction guidance. Experiments on test sets across three major e-commerce stores in different languages (US, DE, FR) demonstrate substantial improvements in catalog data quality, achieving up to 34% increase in recall and 0.8% in precision for attribute value prediction. At catalog entry level, it also achieves up to +43.32% increase in completeness and up to +2.83% in correctness.

We introduce a novel, training free cascade for auto-prompting Large Language Models (LLMs) to assess product quality in e-commerce. Our system requires no training labels or model fine-tuning, instead automatically generating and refining prompts for evaluating attribute quality across tens of thousands of product category–attribute pairs. Starting from a seed of human-crafted prompts, the cascade progressively optimizes instructions to meet catalog-specific requirements. This approach bridges the gap between general language understanding and domain-specific knowledge at scale in complex industrial catalogs. Our extensive empirical evaluations shows the auto-prompt cascade improves precision and recall by 8–10% over traditional chain-of-thought prompting. Notably, it achieves these gains while reducing domain expert effort from 5.1 hours to 3 minutes per attribute - a 99% reduction. Additionally, the cascade generalizes effectively across five languages and multiple quality assessment tasks, consistently maintaining performance gains.