AI agents combine LLMs with external tools to solve complex tasks. While tools extend agents’ capabilities, improper permissions introduce risks such as indirect prompt injection and tool misuse. We characterize these failures as unbalanced tool-driven agency, a unified view in which agents either retain unnecessary permissions (excessive agency) or fail to invoke required tools (insufficient agency), increasing risk and reducing performance. We introduce AgenTRIM, a framework that addresses this imbalance without altering agent reasoning, through complementary offline and online stages. Offline, it reconstructs the agent’s tool interface from code and validates tool behavior via controlled executions and trace analysis. At runtime, it enforces per-step least-privilege access through adaptive capability filtering and isolated validation of tool calls, implicitly decomposing tasks without explicit planning. On the AgentDojo benchmark, AgenTRIM substantially reduces attack success while improving task performance over the baseline, unlike other leading defenses. To assess robustness beyond prompt injection, we conduct additional experiments covering description-based attacks and policy enforcement. Together, these results establish AgenTRIM as a general, capability-preserving framework for mitigating tool-driven risks in LLM-based agents.

An Agentic AI Workflow (AAW), also known as an LLM-based multi-agent system, is an autonomous system that assembles several LLM-based agents to work collaboratively towards a shared goal. The high autonomy, widespread adoption, and growing interest in such AAWs highlight the need for a deeper understanding of their operations, from both quality and security aspects. To this day, there are no existing methods to assess the influence of each agent on the AAW’s final output. Adopting techniques from related fields is not feasible since existing methods perform only static structural analysis, which is unsuitable for inference time execution. We present Counterfactual-based Agent Influence Ranker (CAIR) - the first method for assessing the influence level of each agent on the AAW’s output and determining which agents are the most influential. By performing counterfactual analysis, CAIR provides a task-agnostic analysis that can be used both offline and at inference time. We evaluate CAIR using an AAWs dataset of our creation, containing 30 different use cases with 230 different functionalities. Our evaluation showed that CAIR produces consistent rankings, outperforms baseline methods, and can easily enhance the effectiveness and relevancy of downstream tasks.