Errors in natural language generation, so-called hallucinations, remain a critical challenge, particularly in high-stakes domains such as healthcare or science communication. While several automatic metrics have been proposed to detect and quantify hallucinations, such as FactCC, QAGS, FEQA, and FactAcc, these metrics are often unavailable, difficult to reproduce, or incompatible with modern development workflows. We introduce MIRAGE, an open-source Python library designed to address these limitations. MIRAGE re-implements key hallucination evaluation metrics in a unified library built on the Hugging Face framework, offering modularity, reproducibility, and standardized inputs and outputs. By adhering to FAIR principles, MIRAGE promotes reproducibility, accelerates experimentation, and supports the development of future hallucination metrics. We validate MIRAGE by re-evaluating existing metrics on benchmark datasets, demonstrating comparable performance while significantly improving usability and transparency.

The general public often encounters complex texts but does not have the time or expertise to fully understand them, leading to the spread of misinformation. Automatic Text Simplification (ATS) helps make information more accessible, but its evaluation methods have not kept up with advances in text generation, especially with Large Language Models (LLMs). In particular, recent studies have shown that current ATS metrics do not correlate with the presence of errors. Manual inspections have further revealed a variety of errors, underscoring the need for a more nuanced evaluation framework, which is currently lacking. This resource paper addresses this gap by introducing a test collection for detecting and classifying errors in simplified texts. First, we propose a taxonomy of errors, with a formal focus on information distortion. Next, we introduce a parallel dataset of automatically simplified scientific texts. This dataset has been human-annotated with labels based on our proposed taxonomy. Finally, we analyze the quality of the dataset, and we study the performance of existing models to detect and classify errors from that taxonomy. These contributions give researchers the tools to better evaluate errors in ATS, develop more reliable models, and ultimately improve the quality of automatically simplified texts.