The short version
Most AI tools let you save standing instructions, often called custom instructions, that the AI reads before every chat. Tell it once who you are, how you sound, and how you like things formatted, and you stop re-explaining yourself every time. Setting it up takes about ten minutes.
If you use an AI assistant often, you know this moment. You open it to help draft a client email, and once again, you type: "Write this in a friendly but professional tone. I'm a business owner in San Diego. Don't use emojis. Keep it under 150 words."
It feels like working with a brilliant intern who has total amnesia every morning. You spend half your time re-explaining who you are and how you work before you even get to the task. If you're tired of it, it's time to set up custom instructions, a feature most AI tools have for exactly this.
Custom instructions are a permanent note to your AI.
Think of custom instructions as a note your AI reads before every conversation. Instead of starting from scratch each time, you give it a set of standing rules it remembers across every chat.
It's the difference between a stranger off the street and a longtime colleague who already knows how you talk, what your clients worry about, and which phrases you never use.
Email is where they save the most time.
Email is where most business owners lose the most time. Welcoming a new client, explaining a delay, following up on a quote: the same background gets typed again and again.
With custom instructions, the AI writes in your style from the first draft and skips the corporate filler. Tell it once to sound calm and knowledgeable, like a trusted local expert, and it sticks.
You can also set limits, so you're not trimming a three-page essay down to a simple thank-you note. For example, you might write: "Keep first replies to three paragraphs." Add a short summary of what you offer, too, so the AI never has to ask what you do for a living.
Be specific about who you are and how you write.
The more specific your instructions, the better the results. In my own setup, I describe myself as the founder of a boutique tech agency who prefers simple language over jargon. I mention that I live and work in San Diego, so the AI can add a local touch when it fits.
My formatting rules are just as specific. I tell the AI never to use the long dash known as an em-dash (it uses hyphens or colons instead), and to put the most important information first in every response.
For email, it always writes a clear subject line. When I ask for a follow-up to a client who hasn't replied, it writes it for a three-day gap: polite, but firm about next steps. It doesn't send reminders on its own; it just drafts that way when I ask.
Speed matters, but speed shouldn't cost you your voice. Custom instructions save more than the 30 seconds it takes to retype your background. They make everything you draft, from a LinkedIn post to a project proposal, sound like you. AI stops being a tool you use and starts acting like an assistant who knows your business.
Setting it up takes ten minutes.
Most major AI tools, including ChatGPT and Claude, have a settings area for standing instructions. In most apps, tap your name or profile picture, then look for words like "custom instructions," "personalization," or "preferences." You'll need to be signed in. Once you save your instructions, every new chat starts with that knowledge already loaded.
Keep it to things you'd be comfortable putting on your website. Describe your business and the kinds of clients you serve, but leave out client names, account details, and anything confidential.
Try this
- Open your AI tool's settings and find the section for custom instructions or personalization.
- Write three short paragraphs: who you are and what your business does; who your customers are; and how you want replies written (tone, length, and words to avoid).
- Save, start a new chat, and ask for an email you send every week. Adjust your instructions until the draft needs only light edits.
Nerd note Other ways AI tools remember you
Custom instructions apply to every chat. Many tools also offer projects (a workspace with its own instructions and files, handy for keeping separate clients apart) and memory (details the AI picks up from past conversations). Memory is convenient but less predictable. Instructions you write yourself are the part you fully control, which makes them the best place for your non-negotiables.
Your time is your most valuable asset. If you're still explaining your business to your AI every time you log in, you're losing time you don't have to lose. Take ten minutes today to set your instructions, and stop repeating yourself.
