# Mastra Agents Agents are [[Mastra AI]]'s core primitive: LLM-powered systems that autonomously solve open-ended problems through multi-step reasoning. An agent decides which [[Mastra Tools|tools]] to invoke, maintains [[Mastra Memory|memory]] across turns, and iterates internally until it reaches a conclusion. They suit flexible, exploratory tasks where the steps can't be predetermined, the counterpart to deterministic [[Mastra Workflows|workflows]]. ## Key aspects - Built with instructions, a model, tools, and optional memory - Multi-step reasoning loop with tool calling - Structured output: agents can return typed objects matching a schema (Zod, Valibot, ArkType, JSON Schema) instead of plain text - Processors and guardrails can intercept input/output for validation, PII redaction, moderation, and cost control - Per-request customization via request context (user tier, locale, A/B variants) ## References - https://mastra.ai/docs/agents/overview - https://mastra.ai/docs/agents/structured-output ## Related - [[Mastra AI]] - [[Mastra Workflows]] - [[Mastra Tools]] - [[Mastra Memory]] - [[Mastra Harness]] - [[AI Agents]]