Re-introducing yourself to AI every session is peak inefficiency. Put your identity, style, and goals into a single master prompt, and most routine work automates itself. Today we walk through that structure slowly.
When I advise people on AI tools, one thing everyone misses. They re-introduce themselves to AI every session. "I'm a marketer in my 30s, I mostly do this kind of work, I write in this tone..." Every session starts that way. In a month, that's 60 to 80 repetitions of the same words. I was doing the same in 2023. Then I changed one thing and my day transformed. Today I'll share it. Define your identity with one master prompt. Let me go slowly.
This essay covers three things: why re-introducing every time is broken, what a master prompt is, and how to write one.
Let me show you the structure of our work. Last year I did a full audit of my own workflow. Recorded every task I gave AI for a day and classified them. The result surprised me.
92% of tasks were repetition. Polishing writing in the same tone, drafting emails in the same format, cleaning meeting notes in the same structure, summarizing in the same style. Only 8% required genuinely creative judgment.
And yet I was attaching the same self-introduction to every one of those 92%. "I'm this kind of person with this tone." The peak of inefficiency. 92% repetition with 92% self-intro repetition. I was spending about 40 minutes a day just on the intro. That's 20 hours a month. 240 hours a year. Ten workdays.
What if there were a structure where you write this once? That's the master prompt.
Here's an easy way to see it. Imagine joining a new company.
First day, you submit your résumé and cover letter. Those documents have who you are, what you're good at, and how you work. They get stored in the HR system. Then what happens? You don't re-introduce yourself every time you meet a teammate. The system already knows you. New colleagues reference the document when working with you.
The master prompt is exactly that résumé. Register once with AI — "this is who I am" — and from then on, every conversation starts with the AI reading that first. You've outsourced your self-introduction to AI.
In Claude, you can write this as a file called CLAUDE.md. In ChatGPT, "Custom Instructions" plays the same role. Every AI has a similar structure.
Write it once, use it forever.
That's the one-line definition of a master prompt.
So what do you write? Through three years and five refactors of my own, I found three essential ingredients.
One — Identity. Who am I. Job, field, background, core interests. Two or three sentences. Mine: "I'm a YouTube creator and a university professor. I teach a work philosophy and practical tools for the AI era." Any longer and AI loses the core, so keep it tight.
Two — Style. How do I write. Tone, sentence length, preferred structure, words to avoid. My rules: "Use the formal -ㅂ니다 tone, short sentences, frequent analogies, back things up with numbers."
Three — Goals. What am I working on now. Briefly list 3-5 active projects. "YouTube channel, two books in progress, two courses teaching." This lets AI understand your context and make sensible suggestions.
All three together should fit on one A4 page. Any longer and AI loses steam reading it and misses instructions. I enforce the one-page rule.
Here are my before-and-after numbers.
Drafting one email: without master prompt, average 12 minutes → with, average 3 minutes. 4× faster.
Video script first draft: about 80 min before → about 25 min after. 3.2× faster.
Time from opening new chat to real work: 3 min self-intro every time → 0 min. This one matters most because it repeats dozens of times a day.
All combined, my weekly work time dropped by about 12 hours. 48 hours a month. What did I do with that time? Focused on the 8% of creative judgment. That directly translated into my YouTube performance.
One caution. The purpose of a master prompt is not "hand everything to AI." It's drawing the boundary between what to automate and what to do yourself.
For me, 92% goes to AI. 8% is always mine. What's in that 8% — critical decisions, story's core choices, the emotional connection points with readers, ethical lines. I never delegate these.
Inside the master prompt, write rules like "for these cases, ask me before proceeding." Mine says: "For critical decisions, confirm with me before executing." That one line stops runaway automation. Automate without a boundary and it collapses. Automate with a clear boundary and it becomes leverage.
Once you see the effect at the individual level, there's a next step. A team master prompt. One shared document for the whole team.
On my YouTube production team, three of us work together. Each has a personal master prompt, and on top, we keep one more doc: "shared rules for the 오후다섯씨 channel." Tone, thumbnail rules, banned phrases, upload checklist. Whoever uses AI, the output comes out consistent. Brand consistency becomes systemic.
Even at 2-3 people, a team prompt slashes communication cost. Our weekly team meetings dropped from 3 hours to 1. The prompt does the talking.
A concrete start.
master_prompt.md.That's it. First version: 10 minutes. Don't try to make it perfect. Evolve it as you go. I'm on version 5. I update it every quarter.
One last thing. Write a master prompt once and leave it for three months, and it starts feeling off. Because you change. Interests shift, projects end, new ones start.
I update mine once a quarter. I have a recurring calendar event labeled "prompt review." Takes 30 minutes. That small routine keeps the prompt alive. A dead prompt actually hurts more than it helps. Only a living prompt keeps the automation powerful.
92% of our work is repetition. Re-introducing yourself for every one of those is peak inefficiency. Put identity, style, goals, and boundaries on a single master prompt and you've outsourced your self-introduction to AI. Concentrate energy on the remaining 8% and the quality of output jumps.
Invest 10 minutes tonight. Make a master_prompt.md and walk the 5 steps. Your AI conversations will shift starting tomorrow.
Write once, use forever. Hand your self-intro to AI.
Remember — identity, style, goals.