LLM2Fx-Tools: Tool Calling for Music Post-Production - Doh, SeungHeon; Koo, Junghyun (Tony); Martínez-Ramírez, Marco; Choi, Woosung; Liao, WeiHsiang; Wu, Qiyu; Nam, Juhan; Mitsufuji, Yuki (International Conference on Learning Representations, 2026)