Do Chatbot LLMs Talk Too Much? The YapBench Benchmark
Large language models frequently produce verbose and redundant responses even to simple user requests, imposing unnecessary cognitive load. To address this issue, this work proposes YapBench—a lightweight benchmark that evaluates model over-generation through idealized prompts across three concise scenarios. The study introduces YapScore and YapIndex, novel character-level metrics that do not rely on tokenizers, and constructs an evaluation dataset based on human-annotated minimal sufficient answers. Redundancy is quantified by the character-length difference between model outputs and these minimal answers, enabling consistent cross-model comparisons. Evaluation of 76 assistant models reveals that median redundancy lengths differ by nearly an order of magnitude and uncovers characteristic over-generation patterns, particularly in ambiguous inputs and single-line code tasks.