Bob is a retired accountant. Forty years at a mid-size firm in Ohio. He uses AI to draft emails — to former colleagues, his financial advisor, his grandson's school counselor. Every single time, the AI writes in the wrong tone. Too casual or too corporate. Bob's style is warm but precise. And every session, he explains himself all over again.
Bob would never write "I hope this email finds you well." He'd never end with "Warm regards!" But every new conversation, the AI has no idea who he is. So it defaults to generic corporate filler.
A system prompt (or "custom instructions") is background info the AI reads before every conversation. You write it once, and the AI knows your context from that point forward. No more re-explaining yourself every session.
# Who I am Retired accountant, 40 years at a mid-size firm in Ohio. Methodical and precise. I don't do fluff. # How I write Warm but direct. Short paragraphs. No exclamation marks. I sign emails with just my name, no "Best regards." # What I'm working on Helping my grandson Tommy with college applications (12 schools). Managing my investment portfolio in a spreadsheet. # What I need from AI Don't dumb things down — I understand numbers and logic. Don't be overly cheerful. Match my tone. When I ask about finances, precision not platitudes.
Dear [Name], I hope this email finds you well! I am writing to follow up on the status of the college application process. Please let me know if there is anything I can do to assist. Warm regards!
Hi Sandra — Wanted to check in on Tommy's application status for Ohio State. The priority deadline is January 15 and we're still missing his counselor recommendation. Can you confirm it's been sent? Bob
Same request. Same AI. The only difference is that the second version knows who Bob is.
System prompts aren't just for retirees writing emails. Anyone who uses AI regularly should have one.
# Who I am Freelance illustrator. Moody watercolors, nature themes. Based in Portland. Sell prints and do editorial commissions. # How I communicate Lowercase. Short sentences. No exclamation marks ever. I hate generic influencer-speak — no "amazing," "stunning," or "game-changer." # What I need from AI Help with client emails, invoice wording, and Instagram captions. Match my voice: understated, a little dry, never salesy.
# Who I am Own a 2-chair barbershop in West Philly. Known for fades. Been here 11 years. Eagles fan. Neighborhood spot. # How I communicate Direct, friendly, no corporate speak. I text clients personally. Keep it conversational — like I'm talking to someone in the chair. # What I need from AI Help writing appointment reminders, social posts, and supply orders. Don't make it sound like a chain. We're a local shop. Keep it real.
Settings → Personalization → Custom Instructions
Project settings → Instructions, or start your first message with context
Paste it at the start of your first message in any conversation
Write a system prompt that describes you. Include who you are, how you communicate, what you're working on, and what you need from AI.
Paste this into ChatGPT's Custom Instructions or Claude's Project Instructions to use it for real.
What you learned
Write your context once, use it forever.
System prompts turn every AI conversation from a first date into a working relationship.