Repair, Not Improvement: Decomposing Constrained Decoding in Tool-Call Abstention
A tool-calling router has to pick the right tool when one applies and decline when none does. Restricting the decoder to a grammar over the tool names is the standard remedy for the first, and on small models it buys a large accuracy gain. Recent work separates the loss caused by asking for a format from the loss caused by enforcing it at decode time. The second is small, which made enforcement look nearly free. The same work declines to extend that to function calling, where a constraint decides which answers exist rather than how one is written. Declining to call anything is the answer it most easily removes, and the one a router can least afford to lose. A grammar decides which tokens ...
| Authors | Janghoon Lee |
|---|---|
| Primary category | cs.CL |
| Published | 14 August 2026 |
| Last updated at source | 5 September 2026 |
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