Modern large language models (LLMs) increasingly rely on inference-time planning and external tools to improve reasoning. We benchmark this behavior on two real-world settings: event-centric question answering over graph-structured knowledge (Event-QA) and persuasive response generation in Reddit ChangeMyView (CMV). Using LangChain and LangGraph, we compare a one-shot baseline against a plan-execute-replan agent equipped with task-specific tools (DBpedia SPARQL/lookup/schema exploration, Wikipedia-focused retrieval, and topical web search). We evaluate on 60 examples each from Event-QA and CMV (3 splits of 20), and report both mean end-to-end latency and per-example token cost estimates. We evaluate GPT-4o and GPT-4o-mini under identical workflows and report accuracy and end-to-end latency. On Event-QA, the best tool-augmented configuration improves accuracy (e.g., 47.5\% → 67.5\% for GPT-4o) while increasing latency by orders of magnitude (∼8s →∼317s per example). On CMV, one-shot prompting is strongest (e.g., GPT-4o-mini achieves 75\% at ∼6s), and planning+search increases latency substantially without consistent gains. However, complex multi-tool orchestration exposes failure modes where the smaller model degrades. Overall, the findings highlight the need for task-specific, cost-aware choices of both model size and agent/tooling complexity.
@article{arxiv.2601.02663,
title = {When Do Tools and Planning Help Large Language Models Think? A Cost- and Latency-Aware Benchmark},
author = {Subha Ghoshal and Ali Al-Bustami},
journal= {arXiv preprint arXiv:2601.02663},
year = {2026}
}