Mitigating Hallucinations in Natural Language Generation through Prompt Engineering: A Mechanism- Oriented Narrative Review

Abstract

Large language models (LLMs) can generate fluent and confident responses that are factually incorrect, unsupported by evidence, or inconsistent with the source material. These hallucinations reduce the reliability of LLM-based question answering, summariza tion, dialogue, and information retrieval systems, especially when users rely on generated content for consequential decisions. This narrative review examines prompt engineering as a practical inference-time approach for reducing hallucinations without mod ifying model parameters. Instead of listing individual prompting templates, the paper organizes existing methods according to five functional mechanisms: constraint and evidence grounding, decomposition and verification, multi-path consistency, iterative refinement and tool use, and retrieval-augmented prompting. For each mechanism, the review discusses the hallucination types it is most likely to address, the assumptions required for success, and the conditions under which it may fail. Particular attention is given to Chain-of-Verification (CoVE), which improves auditability by separating answer generation from targeted checking, but remains vulnerable when verification is performed by the same model without independent evidence. The review argues that prom pt engineering should be understood as process-level risk reduction rather than a complete solution. Its strongest use is within evidence-centered system designs that combine retrieval, claim-level verification, calibrated abstention, provenance display, and human review in high-risk contexts.