One-Sentence Definition
An AI agent is a system that uses a language model (or other AI) to autonomously plan, execute multi-step tasks, and interact with external tools and data sources to achieve a goal.
How It Works
A standard chatbot waits for a prompt, generates a reply, and stops. An AI agent takes a goal, breaks it into steps, executes those steps -- often by calling APIs, running code, searching the web, or reading files -- evaluates the results, and iterates until the goal is met or it determines it cannot proceed.
The typical agent loop looks like this: (1) the user states a goal, (2) the language model reasons about what to do first, (3) it selects and calls a tool (a web search, a database query, a code interpreter), (4) it reads the tool's output, (5) it decides the next step, and (6) it repeats until done. This is sometimes called the ReAct (Reasoning + Acting) pattern.
Frameworks like LangChain, CrewAI, AutoGen, and OpenAI's Assistants API provide scaffolding for building agents. Tool use is central -- an agent is only as capable as the tools it can access. A coding agent might have access to a terminal and file system. A research agent might have web search and document retrieval. A customer-service agent might connect to a CRM and order-management system.
Why It Matters
Agents represent the shift from AI as a text generator to AI as a worker. In 2026, companies are deploying agents to handle customer support tickets end-to-end, automate software development workflows (Devin, Claude Code, Cursor), conduct research across dozens of sources, and manage repetitive business processes.
The challenge is reliability. Agents can make mistakes at any step, and errors compound across a multi-step workflow. This is why most production agents include human-in-the-loop checkpoints, guardrails that limit which actions the agent can take, and logging that makes every decision auditable.
Key Takeaway
An AI agent uses a language model to autonomously plan and execute multi-step tasks with tools, moving AI from passive text generation to active problem-solving.
Part of the AI Weekly Glossary.