---
title: 'AI agent'
description: 'A software system in which a model interprets a goal or input, decides among actions, uses tools or other capabilities, observes results, and continues until completion, handoff, or termination.'
canonical_url: 'https://darkfactory.dev/glossary/ai-agent'
markdown_url: 'https://darkfactory.dev/glossary/ai-agent.md'
collection: glossary
date_published: '2026-08-03T00:00:00-04:00'
date_modified: '2026-08-26T00:00:00-04:00'
---

# AI agent


## Definition

An AI agent is a software system in which a model interprets a goal or input, chooses among actions, uses tools or other capabilities, observes the results, and continues until completion, handoff, pause, or termination.

The agent is the whole operating system, not the model alone. Its behavior depends on the harness that supplies instructions, state, tools, permissions, control flow, budgets, and recovery. Calling an application an agent should therefore identify the action loop and the authority attached to it.

Definitions vary across vendors and research communities. Some call any goal-directed model interaction an agent; others reserve the word for systems that can use tools over multiple steps. In this glossary, the repeated action-and-observation loop is the threshold.

## Distinguish it from nearby terms

An agent has an action loop. A workflow can execute a fixed sequence without model discretion. A chatbot may only generate a response. A model by itself has no independent tools, state, or permissions.

## Check your understanding

A model writes a travel plan in one response. That is generation. If the surrounding system searches flights, compares results, asks for missing constraints, and holds an itinerary for approval, the application is operating as an agent.

## Also called

agent, LLM agent

## Related factory areas

- [Orchestration, state, concurrency & recovery](https://darkfactory.dev/factory/orchestration-state)

## Evidence and further reading

- [NIST AI 100-2: Adversarial Machine Learning](https://csrc.nist.gov/pubs/ai/100/2/e2025/final)
- [Google Machine Learning Glossary](https://developers.google.com/machine-learning/glossary/)
- [OpenAI: A Practical Guide to Building Agents](https://openai.com/business/guides-and-resources/a-practical-guide-to-building-ai-agents/)
- [The Anatomy of an Agent Harness](https://www.langchain.com/blog/the-anatomy-of-an-agent-harness)