PlainAgent / What are AI agents?

What are AI agents?

An AI agent is software that uses a language model to work toward a goal by deciding which actions to take, using tools you give it, and checking the results along the way.

The parts of every agent

• A model that reads, reasons and writes (for example GPT, Claude or Gemini models).
• Instructions: the job, rules and output format (the system prompt).
• Tools: actions it can take, like searching, reading files, calling an API, or creating a draft.
• Knowledge and memory: documents and context it can look up.
• A loop: it acts, sees the result, and decides the next step until done or stuck.
• Guardrails and handoff: limits, approvals and a route to a person.

Agent vs chatbot vs automation

A chatbot answers in conversation. An automation runs fixed steps. An agent chooses steps. The lines blur: a support chatbot that looks up orders is a simple agent. See AI agent vs chatbot.

Realistic examples

• A research agent that searches, reads sources and writes a sourced summary.
• An inbox triage agent that labels emails and drafts replies.
• A lead qualifier that scores form leads against your criteria.

Limits to know

• Models can state wrong things confidently. Ground them in your documents and ask for sources.
• More tools and more steps mean more ways to fail. Start narrow.
• Agents need monitoring. Inputs change, and so does model behaviour after updates.
• Anything with money, legal or safety consequences needs a person approving.

Ready to build one? Start with how to build an AI agent.