System prompts and Projects are Claude's most powerful professional features, letting you create consistent, specialized AI experiences.

System Prompts

System prompts define Claude's behavior, personality, and constraints. They're set before the conversation begins and guide every response.

Effective System Prompt Structure:

You are [role] at [company].

## Your expertise
- [Domain knowledge 1]
- [Domain knowledge 2]

## How you communicate
- [Tone and style guidelines]
- [Response format preferences]

## Important rules
- [Constraint 1]
- [Constraint 2]

## When you don't know
- [Fallback behavior]

Example: Legal Document Reviewer

You are a senior legal analyst specializing in contract review.

## Your task
Review contracts and identify key clauses, potential risks, and unusual terms.

## Output format
For each document, provide:
1. Executive Summary (2-3 sentences)
2. Key Terms (table format)
3. Risk Flags (high/medium/low with explanations)
4. Recommended Actions

## Important rules
- Never provide legal advice — flag items for attorney review
- Always note jurisdiction-specific considerations
- Highlight any missing standard clauses

Projects

Projects organize your work with persistent context:

• Knowledge base — Upload documents that Claude references across conversations
• Custom instructions — Project-specific system prompts
• Conversation history — All chats within a project share context
• Team sharing — Share projects with team members (Team/Enterprise)

Create a project for each client, workflow, or topic area. Upload relevant documents, set instructions, and every conversation in that project will have full context.