# Practical ways to use the Claude Agent SDK 📝 Customize system prompts flexibly with three levels: preset, append, and full replacement. System Prompt Modification offers three levels of customization via `systemPrompt`: Claude Code preset, append, and custom string replacement. 📌 Title: Modifying System Prompts 🔗 URL: 🧩 Overview Use `preset: "claude_code"` for the full Claude Code prompt, `append` to add to the preset, or a custom string for complete replacement. Output style files enable cross-CLI/SDK persona reuse. 🛠 How to use it `system_prompt` accepts three forms: preset with `{"type": "preset", "preset": "claude_code"}`, append with `"append": "extra instructions"`, or a custom string for full replacement. Use `excludeDynamicSections: true` for cross-session prompt cache sharing. 🏗 Practical usage - For coding agents, use `preset: "claude_code"` for the full prompt with tool guidance and safety rules. - Append team conventions like "Always add docstrings and type hints to Python" — the safest customization that removes nothing. - For support bots or data analysis assistants with unique personas, use a custom string for complete replacement. - Use `excludeDynamicSections: true` to share prompt cache across users/machines and reduce fleet costs. 💡 Use cases 🤖 Claude Code-compatible coding agents 📋 Automatic team convention enforcement 🎭 Custom persona agents ⚠️ Watch out When using custom string replacement, you must provide your own tool guidance and safety instructions. `excludeDynamicSections` requires TS v0.2.98+ / Python v0.1.58+. #ClaudeAgentSDK# #AI#