# Part 2: Core Capabilities

> 🧠 Systematically master all the core technical capabilities needed to build Agents — from tool calling to reinforcement learning training.

This is the most substantial part of the book, containing 7 chapters that cover the complete capability progression chain for Agents.

| Chapter | Content | Analogy |
|---------|---------|---------|
| **Chapter 4** Tool Calling | Function Calling, custom tools | The Agent's "hands" |
| **Chapter 5** Memory System | Short-term / long-term / working memory | The Agent's "brain" |
| **Chapter 6** Planning & Reasoning | ReAct, task decomposition, reflection | The Agent's "thinking" |
| **Chapter 7** RAG | Document retrieval, vector databases | The Agent's "knowledge base" |
| **Chapter 8** Context Engineering | Window management, attention budget | The Agent's "information hub" |
| **Chapter 9** Skill System | Skill encapsulation, learning & discovery | The Agent's "skill tree" |
| **Chapter 10** Agentic-RL | SFT, PPO, DPO, GRPO | The Agent's "self-evolution" |

**Capability Progression**: Use tools → Remember → Think → Retrieve → Manage context → Encapsulate skills → Self-evolve

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*Start learning: [Chapter 4: Tool Calling](./chapter_tools/README.md)*
