# Single Agent

> Understand how one Agent is determined by model, tools, and context.

At the core, every Agent is determined by three things:

1. Model

The model is the Agent's brain.

2. Available tools

Tools are the Agent's hands and feet.

3. All existing context

Context includes the system prompt and every relevant user / assistant message. It is the Agent's mind.

All context affects the Agent's behavior. The system prompt matters, but it is never the whole story.

## Expanded, one by one [#expanded-one-by-one]

* [Model](./model): pick the right brain for each Agent's role.
* [Tools](./tools): what the Agent can reach and change.
* [Context](./context): build a clear mind from three kinds of context — constraints, information, task.
* [ReAct](./react) and [Action Sequence](./action-sequence): how a single Agent reasons while acting, and breaks a complex goal into executable stages.

Source: https://the-zeroth.com/en/docs/multi-agent-architecture/single-agent