Comparing mental health questionnaires like the PHQ-9 and WEMWBS can surface invaluable insights for psychological and social research. However, this comparison, known as harmonisation, is often time-consuming and subjective. Harmony, a revolutionary tool for questionnaire comparison, can streamline this process for the PHQ-9 vs WEMWBS comparison. This tool utilizes natural language processing and generative AI models to harmonise questionnaire items, even in different languages. Harmony’s significant contribution to the harmonisation process shines when comparing the PHQ-9 and WEMWBS instruments. The PHQ-9 questionnaire addresses depressive symptoms, while the WEMWBS questionnaire is oriented toward positive mental wellbeing. By using Harmony, researchers can select these specific instruments from Harmony’s extensive database. Once the PHQ-9 and WEMWBS instruments are selected, Harmony employs large language models to present a percentage match between each item. This PHQ-9 vs WEMWBS comparison can garner a greater understanding of mental health trends and contribute significantly to quantitative research. The applicability and efficiency of Harmony in comparing PHQ-9 and WEMWBS can streamline and improve research quality. As the tool also accommodates multiple languages, its inclusive approach broadens its effectiveness across global research. For researchers who intend to conduct a PHQ-9 vs WEMWBS comparison, or any other pair of questionnaires, Harmony serves as a reliable, user-friendly, and time-efficient solution. As research scope and depth continue to expand in contemporary society, Harmony continues to bridge the gap between complex comparisons.