Woojung Song

M.S. in Data Science, Seoul National University

Research Interests

I work on AI agents and value alignment. As LLMs have become increasingly capable, they are entering everyday life through tool use, autonomous decision-making, and direct interaction with people. This raises a natural question: how do we ensure these systems behave in ways that reflect diverse human values, and how do we even know if they do?

  1. Tool-Use Agents. Enabling language models to effectively use tools so they can tackle more real-world tasks and assist users across diverse scenarios.
  2. Value Alignment. As LLMs take on more roles in society, we need ways to understand and evaluate what values they express. I work on building better frameworks for measuring this, moving beyond surface-level benchmarks toward methods that capture how models actually behave in context.

If any of this resonates, feel free to reach out at opusdeisong@snu.ac.kr.

Publications

Full list on the Publications page.

Agents

Don't Adapt Small Language Models for Tools; Adapt Tool Schemas to the Models

ACL 2026 (Main)

Jonggeun Lee*, Woojung Song*, Jongwook Han, Haesung Pyun, Yohan Jo  Co-first

Proposes PA-Tool, a training-free method that renames tool schema components to align with small language models' pretraining familiarity, achieving up to 17% improvement on tool-use benchmarks without model retraining.

PA-Tool overview

Value Alignment

Human Psychometric Questionnaires Mischaracterize LLM Psychology: Evidence from Generation Behavior

Under Review, 2026

Woojung Song*, Dongmin Choi*, Yoonah Park, Jongwook Han, Eun-Ju Lee, Yohan Jo  Co-first

Shows that LLM psychological profiles from standard questionnaires diverge from profiles derived from actual generation behavior on real user queries.

Questionnaire vs generation behavior

Value Alignment

Quantifying Data Contamination in Psychometric Evaluations of LLMs

EACL 2026 (Findings)

Jongwook Han*, Woojung Song*, Jonggeun Lee*, Yohan Jo  Co-first

A systematic framework to measure data contamination across item memorization, evaluation memorization, and target score matching in psychometric LLM benchmarks.

Value Alignment

Value Portrait: Assessing Language Models' Values through Psychometrically and Ecologically Valid Items

ACL 2025 (Main)

Jongwook Han*, Dongmin Choi*, Woojung Song*, Eun-Ju Lee, Yohan Jo  Co-first

Proposes the Value Portrait framework for evaluating LLM values using items from real user-LLM interactions, finding across 44 LLMs that they emphasize Benevolence, Security, and Self-Direction.

Value Portrait framework

Applied ML

Interpretable Prediction of Private Brand Purchases by Pet Type in E-Commerce for Consumer Behavior Analysis Using Real-World Transaction Data

PeerJ CS, 2025

Jaehyuk Lee*, Woojung Song*, Jina Kim, Eunchan Kim  Co-first