# Agents

Everything about building a single agent — from the first `Agent` instance to advanced cognitive composition.

## Sections

- [Fundamentals](fundamentals/index.md) — Agents, roles, actions, and the event bus. Start here.
- [Behavior](behavior/index.md) — Prompts, output parsing, streaming, memory, variants.
- [Reliability](reliability/index.md) — Resilience, error handling, schema identity.
- [Advanced](advanced.md) — Cognitive support, planner/reasoner handles, ensemble execution.

## Related

- [Multi-Agent](../multi-agent/index.md) — When one agent isn't enough.
- [Capabilities](../capabilities/index.md) — Tools, intelligence, RAG, LLM.
- [Agent-level action RAG](../capabilities/rag/agent-knowledge.md) `@AgentSpec.knowledge()` / `retrieval()` (`@since 0.14.0`).