What is an Agent Loop?

2 min read Updated

The agent loop is the fundamental execution cycle of an AI agent: observe the current state, think about what to do (using an LLM), take an action (call a tool), observe the result, and repeat until the task is complete or a stop condition is met.

WHY IT MATTERS

Every AI agent, regardless of framework or architecture, runs some variant of the agent loop. At its simplest: get user input → call LLM → if LLM wants to use a tool, execute it → feed result back to LLM → repeat until LLM returns a final response.

The agent loop is deceptively simple but the details matter. How many iterations before you force a stop? How do you handle tool execution failures? When do you escalate to a human? These decisions shape agent behavior more than the choice of LLM.

For financial agents, the loop is where spending happens. Each iteration could trigger a transaction. Without controls, a runaway loop could execute dozens of transactions in seconds — burning through a budget before anyone notices.

HOW POLICYLAYER USES THIS

PolicyLayer intercepts the 'act' phase of the agent loop for financial operations. Before any transaction executes, it passes through policy validation. This adds a policy checkpoint to every iteration of the loop without modifying the agent's core logic.

FREQUENTLY ASKED QUESTIONS

How do you prevent infinite agent loops?
Set a maximum iteration count, implement total runtime limits, use token budgets, and add circuit breakers that halt the loop if the agent seems stuck. For financial agents, spending limits naturally bound loop iterations.
What's the typical structure of an agent loop?
1. Receive input/observation. 2. Call LLM with context + available tools. 3. If LLM returns a tool call, execute it and go to step 2. 4. If LLM returns a final response, return it to the user.
Can you customize the agent loop?
Yes. Frameworks like LangGraph let you define arbitrary graph-based loops. Even with simpler frameworks, you can add middleware (logging, policy checks, validation) at each step of the loop.

FURTHER READING

Enforce policies on every tool call

Intercept is the open-source MCP proxy that enforces YAML policies on AI agent tool calls. No code changes needed.

npx -y @policylayer/intercept
github.com/policylayer/intercept →
// GET IN TOUCH

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