AgentCheck: A Reproduce-Intervene-Mitigate Workbench for LLM Agents over MCP

Jul 14, 2026

AgentCheck is an open-source web workbench that enables systematic testing of LLM agents using tools via an MCP server. It records tool responses, injects 12 types of faults, and allows developers to re-run agents to evaluate the effectiveness of mitigations. In tests across five agents, the best agent passed 105 out of 120 scenarios, while the weakest passed 77, with most failures involving silent misuse of incorrect tool outputs.

Why it matters: AgentCheck addresses a critical gap in reliability testing by providing a reproducible and controlled environment to evaluate and improve the robustness of tool-using LLM agents before deployment.

Full story at: arXiv Software Engineering ↗