04 Agent Fundamentals

Phase 2 - Agent Core
Stage 4 of 14. Previous: Stage 3 - Prompt Engineering. Next: Stage 5 - Tools and Actions.

Goal

Understand the basic agent loop and how agents use tools to work toward goals.

Learn

• Agent Loop
• ReAct Pattern
• Reasoning and Planning
• Acting and Observation
• Stopping Criteria
• Tools Overview

Build

Implement a simple ReAct-style loop from scratch with one or two safe tools.

Exit Criteria

• You can describe observe, reason, act, observe, and finish.
• You can explain why stop conditions are required.
• You can distinguish a fixed workflow from a more autonomous agent.

Checkpoint

Use the Stage 4 checkpoint before moving on.

Test

Use the QAs: 04 Agent Fundamentals to check your understanding of every topic in this stage.

Interview

For deeper study or hiring, use the interview pages with interviewer rubrics:

• Junior Interview: Agent Fundamentals — friendly, example-driven questions for learners.
• Senior Interview: Agent Fundamentals — open-ended, trade-off and design questions.