How to Build Claude Agents: A Complete Guide to CLAUDE.md

CLAUDE.md files are the secret to building powerful, reliable AI agents with Claude Code. In this guide, you'll learn everything you need to create your first agent configuration.

What is a CLAUDE.md File?

A CLAUDE.md file is a configuration file that defines how an AI agent should behave. It includes instructions, capabilities, rules, and constraints that shape the agent's responses and actions.

Think of it as a "personality profile" for your AI agent - it tells Claude what it can do, what it should never do, and how it should approach tasks.

The Structure of a CLAUDE.md File

A well-structured CLAUDE.md file typically includes these sections:

# Agent Name

Brief description of the agent's purpose.

## Core Principles
- Principle 1
- Principle 2
- Principle 3

## Capabilities
- What the agent can do
- Tools it has access to

## Negative Prompt (Critical Rules)

### NEVER DO
- Rule 1
- Rule 2

### ALWAYS DO
- Positive rule 1
- Positive rule 2

The Power of Negative Prompts

Negative prompts are arguably the most important part of your CLAUDE.md file. They define boundaries and prevent unwanted behaviors.

Key insight: Telling an AI what NOT to do is often more effective than telling it what to do. Negative prompts create guardrails that keep the agent on track.

Essential Negative Prompts

• NEVER store or display passwords in plain text
• NEVER modify code without reading it first
• NEVER repeat the same action more than 3 times
• NEVER claim an action succeeded without showing output
• NEVER make financial transactions without verification

Preventing Agent Loops

One of the most common problems with AI agents is getting stuck in repetitive loops. Your CLAUDE.md should include anti-loop rules:

## Loop Prevention

- Do not repeat the same action more than 3 times
- Do not take more than 3 screenshots per task
- If blocked, stop and report - do not keep retrying
- Do not poll or refresh repeatedly while waiting

Best Practices

1. Start with security rules - These are non-negotiable and should be at the top of your configuration.
2. Be specific - Vague instructions lead to vague behavior. Use concrete examples.
3. Include verification steps - Always have the agent confirm its actions completed successfully.
4. Add escalation rules - Define when the agent should stop and ask for help instead of continuing.
5. Test and iterate - Your first CLAUDE.md won't be perfect. Observe behavior and refine over time.

Getting Started with AgentForge

Instead of writing your CLAUDE.md from scratch, use our free builder tool. It includes pre-built capabilities and rulesets that you can customize for your use case.

Conclusion

Building effective AI agents requires careful configuration. A well-crafted CLAUDE.md file is the foundation of a reliable, safe, and productive agent. Start with strong negative prompts, add specific capabilities, and iterate based on real-world performance.

With AgentForge, you can skip the trial-and-error phase and start with battle-tested configurations from real production systems.