System prompts

What is a system prompt?

A system prompt is an instruction you give Claude before the conversation starts. It is invisible in the chat but controls tone, role, format and behaviour throughout the entire dialogue. Think of it as giving a new employee a thorough briefing before their first day.

💡 Technically explained:
In the Claude API the system prompt is sent as a separate "system" field, separate from the user messages. In Claude.ai you can set it in Projects under "Project instructions".

Anatomy of a good system prompt

✅ System prompt template:
1. Role — who is Claude in this context?
2. Context — what is the situation and audience?
3. Tone — formal, informal, technical, pedagogical?
4. Format — bullet lists, short answers, markdown?
5. Constraints — what should Claude NOT do?

Common mistakes

⚠️ Avoid these mistakes:
— System prompt that is too long with conflicting instructions
— Vague instructions like "be helpful" without concrete context
— Forgetting to update the system prompt when context changes
— Trying to "lock" Claude with excessive restrictions

"A good system prompt is like a good employment contract — precise enough to give direction, flexible enough to allow judgement." — Principle for system prompt design

🎯 Test your knowledge

Test yourself — completely optional, but fun! 🎯

Question 1 of 3

What is a system prompt?

An instruction given before the conversation starts — invisible in the chat but controls tone, role and behaviour throughout the entire dialogue.

Question 2 of 3

What five elements should a good system prompt contain?

Role, context, tone, format and constraints — these five elements give Claude precise and consistent behaviour.

Question 3 of 3

Where do you set the system prompt in Claude.ai?

In Claude.ai Pro and Team you set the system prompt under Projects → Project instructions.

System prompts

What is a system prompt?

Anatomy of a good system prompt

Common mistakes

🎯 Test your knowledge

Question 1 of 3

Question 2 of 3

Question 3 of 3

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