ToolBench-X: Benchmarking Tool-Using Agents Under Unreliable Environments
The authors introduce ToolBench-X, a new benchmark designed to evaluate large language model agents under recoverable tool-environment unreliability. Unlike existing benchmarks that assume clean and stable environments, this framework injects five structured hazard types: Specification Drift, Invocation Error, Execution Failure, Output Drift, and Cross-source Conflict. The dataset contains executable multi-step tasks across diverse domains with deterministic tools and canonical final answers for automatic evaluation. Crucially, every injected instance remains solvable through valid recovery paths such as retrying, fallback, or verification. Experiments reveal a substantial reliability gap where agents performing well with reliable tools often fail under these hazards. Further analysis indicates that failures stem from limited hazard diagnosis and ineffective recovery rather than tool-use volume or inference budget. Targeted recovery hints successfully recover many failed tasks, whereas test-time scaling yields more limited gains. These findings suggest that evaluation must shift focus from function-call accuracy to task completion in unreliable environments.