Interactional Fairness in LLM Multi-Agent Systems: An Evaluation Framework

As large language models (LLMs) are increasingly used in multi-agent systems, questions of fairness should extend beyond resource distribution and procedural design to include the fairness of how agents communicate. Drawing from organizational psychology, we introduce a novel framework for evaluating Interactional fairness (IF), encompassing interpersonal respect and the adequacy of justifications in LLM-based multi-agent systems (LLM-MAS). We extend the theoretical grounding of Interactional fairness to non-sentient agents, reframing fairness as a socially interpretable signal rather than a subjective experience. We then adapt established tools from organizational justice research, including Colquitt’s Scale and the Critical Incident Technique, to measure fairness as a behavioral property of agent interaction. We validate our framework through a pilot study using controlled simulations of a resource negotiation task. We systematically manipulate tone, explanation quality, outcome inequality, and task framing (collaborative vs. competitive) to assess how interactional fairness influences agent behavior. Results show that tone and justification quality significantly affect acceptance decisions—even when objective outcomes are held constant—and that their influence varies with context. This work lays the foundation for Interactional fairness auditing and norm-sensitive alignment in LLM-MAS.