How do I prevent an AI agent from getting stuck in infinite tool-calling loops?

To prevent an AI agent from getting stuck in infinite tool-calling loops, implement explicit iteration budgets and robust error handling with defined termination conditions.

Here are concrete controls:

• Implement Iteration Budgets: Each agent, including subagents, should have an IterationBudget that limits the total number of iterations (model calls and tool dispatches) it can perform within a "turn" (one user message to a final assistant reply). This budget should be thread-safe and reset at the beginning of each turn to prevent previous activity from starving subsequent interactions. This addresses the OWASP LLM Top 10 risk of "Rate Limit and Resource Exhaustion".
• Refund Iterations for Internal Steps: Distinguish between user-visible reasoning steps and internal runtime bookkeeping steps (e.g., programmatic tool calling) by refunding iterations for the latter. This ensures agents don't prematurely exhaust their budget on non-user-facing operations.
• Define Clear Termination Conditions: The agent loop should explicitly check for conditions to halt the turn, such as the model returning final text or budgets/guardrails being met. The run_conversation loop should repeat until the model stops requesting tools or the iteration budget is exhausted.
• Utilize a State Machine for Loop Control: Employ a state object with a transition field to record why the previous iteration continued. This allows the next iteration to make informed recovery decisions and prevents infinite loops by avoiding repeated attempts at the same recovery strategy.
• Implement Tool Guardrails and Hooks: Tool execution should pass through layers of guardrails with per-turn resets and halt decisions. This includes pre-tool-call hooks for user confirmation on destructive edits and post-tool empty-response retries when the model stalls. This aligns with the NIST AI RMF function of "Govern" and "Map" by ensuring responsible behavior and understanding of AI system capabilities.
• Validate Tool Call Outputs: Implement output schema validation for tool calls. If a tool call is expected to produce structured output, validate it. Refusing to proceed on schema violation can interrupt many attacks and prevent agents from getting stuck due to malformed responses. This addresses the OWASP LLM Top 10 risk of "Tool Misuse and Unsafe Tool Calls".