Core Concepts

Core Concepts Deep Dive

A 3-minute overview of Models, Agents, Harnesses, Memory, and Tools — the building blocks of AI agents

Before building with agents, it helps to have clear mental models for the key pieces. Think of these concepts like understanding the parts of a car before you learn to drive.

🧠 Models→🤖 Agents→🔧 Agent Harnesses→💾 Memory & Context→⚡ Tools & Actions→

The three-layer mental model

Every AI agent system has three layers:

┌─────────────────────────────────┐
│         YOUR APPLICATION        │  ← What users see and interact with
├─────────────────────────────────┤
│         AGENT HARNESS           │  ← Orchestration, memory, tools, routing
├─────────────────────────────────┤
│         AI MODEL                │  ← The reasoning engine (Claude, GPT, etc.)
└─────────────────────────────────┘

You don't have to build all three yourself — that's what the tools in this cookbook are for. But understanding what lives at each layer makes you dramatically better at both using and building agent systems.

History Models