arXiv AI
Oct 9

Structure Tax: How Structured Output affects LLMs Performance

The paper investigates the so‑called ‘structure tax’ that is often attributed to constraining large language model outputs to structured formats like JSON or XML. By evaluating various models, datasets, and schema designs, the authors find that the accuracy loss depends more on how the schema is organized than on the presence of structure itself. Specifically, reasoning‑first field ordering can match or surpass free‑form accuracy, whereas answer‑first ordering leads to significant drops, especially in smaller models. The study also shows that well‑designed schemas improve confidence calibration and the separability of correct versus incorrect representations in transformer layers.

By Vineet Kumar, Kanishka, Bhuvanesh Mandora
arXiv Computation and Language
5d ago

SERIAL-7: Deriving, Realizing, and Preserving Machine-Verifiable Outputs Across Representations

SERIAL-7 is a Korean‑English benchmark that evaluates large language models on their ability to generate machine‑verifiable structured outputs across seven representations. It introduces an executable verification framework that separates semantic derivation (Derive), constrained artifact generation (Realize), and cross‑representation preservation (Preserve), using 177 validated artifacts and 43 atomic representation constraints. The benchmark shows that reliable structured generation requires explicit, executable verification of how artifacts are realized and preserved, as evidenced by varying compliance rates across ten models.

By Youngkyung Seo, MiHyeon Kim, Jisoo Lee, Hwijung Ryu