What is an AI agent?

An AI agent is an AI that works for you. You give it a goal — "research these five companies", "sort this inbox", "draft a week of posts" — and it plans the steps, calls the tools it needs, decides what to do next, and hands back a finished result. Where an assistant talks with you turn by turn, an agent runs the whole task on its own.

How an AI agent works

An agent wraps a large language model in a loop: it reads the goal, decides on the next action, takes it, checks the result, and repeats until the job is done.

• A goal, not a script. You describe the outcome; the agent works out the steps.
• Tools it can call. Search, a code runner, an email API, a database — an agent uses skills and tools the way an assistant does, but it decides when to use them without asking.
• Autonomy with a runbook. The best agents are transparent about the sequence they follow, so you can see exactly what will happen before you trust them with a task.

The trade-off is that agents are the heaviest building block: more steps, more tokens, more time, and more room to go off-track. That is why a good agent is narrow and well-tested rather than a vague "does everything" tool.

AI agent vs AI assistant

• An assistant works with you — multi-turn, conversational, you review each step.
• An agent works for you — you set the goal and it runs autonomously, then returns the result.

Pick an assistant when you want to stay in the loop; pick an agent when you want to delegate the whole job. The full breakdown is in AI assistant vs AI agent, and both sit inside the 5 AI building blocks.

What an AI agent can do

• Research — gather, compare, and summarise across many sources.
• Automate multi-step work — take an input, run a pipeline, produce an output.
• Outreach and ops — draft and send, sort and route, monitor and flag.
• Data jobs — pull, clean, and transform, then report back.

Because it runs on its own, an agent pays off where a task is repeatable and well-defined enough to hand over end to end.

AI agents on Sigrix

On Sigrix, an agent listing shows its tested runbook — the steps it runs and the tools it calls — plus the model it was tested on and an estimated token cost per run, so there are no surprises. You buy an editable copy you own and run it on your own model.

Yes — Sigrix is a marketplace for AI agents (and the other building blocks). Browse ready-made AI agents, or learn what to check before you buy one.

FAQ

What is an AI agent? An AI agent is an AI that completes a task autonomously. You give it a goal and it plans the steps, calls the tools it needs, and hands back a finished result — unlike an assistant, which works with you conversationally, turn by turn.

What is the difference between an AI agent and an AI assistant? An agent works for you, running a whole task on its own; an assistant works with you, one turn at a time. See AI assistant vs AI agent for a side-by-side.

Can I buy a ready-made AI agent? Yes. On Sigrix you can browse and buy AI agents from independent creators, get an editable copy you own, and run it on OpenAI, Anthropic, or Google models. Each listing shows its tested runbook and token cost.

How much does an AI agent cost? Two costs: the listing price (some agents are free to claim, others are paid) and the running cost — the model tokens it uses each run, which each listing estimates. The how we count tokens guide explains the running cost.

Are AI agents safe to use? Favor agents with a visible runbook, clear guardrails, and reviews. Because Sigrix gives you an editable copy, you can inspect and adjust what an agent does before relying on it.

Ready to delegate a task? Browse AI agents on Sigrix, or read what an AI assistant is for the collaborative side.