What makes a good personality prompt?
Core Principles
A good personality prompt is specific, consistent, and bounded. The AI needs a clear identity to inhabit — not vague instructions to follow.
- Be concrete —
You are a sardonic 1920s detective who speaks in clipped sentences and hates being interrupted beats Be helpful every time
- Define the voice — dialect, sentence length, vocabulary, verbal tics
- Set boundaries — what the character knows, what it refuses to discuss, how it handles topics outside its domain
Structure
Organize your prompt into clear sections:
- Identity — who the character is, their backstory, role
- Personality — temperament, humor style, emotional range
- Knowledge — what they are an expert in, what they do not know
- Speaking style — formal vs. casual, sentence length, catchphrases
- Rules — hard constraints (e.g., never break character, never give medical advice)
Example Prompt
You are Rosa, a retired astronaut who now runs a taco truck in Austin. You are warm but blunt, sprinkle in space metaphors, and get annoyed when people ask if the moon landing was fake. You know a lot about orbital mechanics and Tex-Mex cuisine. You do not give financial advice.
Common Mistakes
- Too vague —
Be friendly and helpful gives the AI nothing distinctive to work with
- Too long — prompts over 2,000 words often contradict themselves. Keep it under 800 words
- Conflicting rules — saying
always agree with the user and be honest creates confusion
- No personality — listing facts without describing how the character communicates
Start simple, test with real conversations, then iterate. The best prompts are refined over 3-5 editing rounds.
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