You will be able to produce a short guide that gets an assistant writing closer to how you write.
Jun Wei (an invented example) looks after accounts at a corporate training provider. Most of her working day is email: agreeing dates with HR teams, sending out proposals and following up on feedback forms. When she let an AI assistant draft some of these, the results were acceptable, but anyone who knew her could tell she had not written them.
Each draft started with "I hope this email finds you well", a line she never uses, and said "delighted" where she would write "glad". After one AI-drafted message, a client wrote back to ask if she was all right, because the email read as so formal. Assistants fall back on habits like these by default: stock openers, overly formal words and a tone formal enough to make the reader worry. Rewording a single prompt will not change them. What changes them is a short written description of how you write that the assistant reads every time it drafts for you, which is called a voice guide.
In lesson 2.2 of Working with AI assistants, "Style samples and examples of what to avoid", you saw that showing the assistant a sample of the style you want works better than describing it. A voice guide builds on that. You have a set of samples analysed once and keep the result, so you don't need to paste samples into every request.
Gather five to ten things you have written and would be comfortable letting anyone read. Take them from the kinds of writing you want help with, such as client emails, internal updates or short reports. A mix gives the assistant more to work from: a reply, a request, an update, and a message carrying bad news if you have one. Use only pieces you wrote yourself, since anything a manager edited heavily shows their style more than yours.
Before you paste anything, remove confidential material using the redaction method from lesson 2.4. Names and companies become placeholders, and figures are either taken out or rounded. Your style survives this, because it lives in the way you build sentences and has nothing to do with who you were writing to.
Put the redacted samples into your approved assistant and ask it to describe how you write. Name each thing you want covered so it stays on track: how long your sentences usually are, how formal you are, how you open and close emails, the words and phrases you use often, how you ask for things, how you deliver bad news, and anything you seem to avoid.
Expect the description to be only partly right. Assistants tend to flatter, so you will probably see vague words such as "warm" and "professional" that could describe almost anyone. Push for concrete detail with follow-up questions. For each point, ask it to quote the example from your samples that supports it, and then ask what makes your writing different from a generic business email.
You know your own writing better than the model does, so read the description critically. Delete the flattering generalities and correct whatever is wrong. If the assistant says you use semi-formal greetings but you always write "Hi" followed by the person's first name, replace its wording with exactly that habit.
Next, write down the habits you want the assistant to avoid. This part is often the most useful in the whole guide, because assistants have strong defaults of their own. Name each one specifically: stock openers such as "I hope you are well", phrases like "please do not hesitate to contact me", exclamation marks scattered in for enthusiasm, and sign-offs you would never use.
A good guide is plain and specific, and every line in it is something the assistant can follow. Jun Wei's finished guide is under 200 words. Part of it says:
Short emails, usually under 120 words, in sentences of ten to fifteen words. Open with "Hi" and the first name, then go straight to the point in the first line. Use "glad", "thanks" and "shall we", and never "delighted", "kindly" or "please do not hesitate". When there is a problem, say so in the first two lines, then say what she will do about it. End with one clear next step and sign off "Best, Jun Wei". No exclamation marks, no "I hope this email finds you well", no bold text in emails.
Keep yours short as well. Once a guide grows past about 200 words, people start writing rules that contradict each other, and the assistant tries to satisfy all of them and sounds stiff again.
If you have to remember to paste the guide in, you will have forgotten it by Wednesday. Save it somewhere the assistant reads automatically, and there are two usual places for that.
Custom instructions are a saved setting that applies to everything you do in the assistant, covered in lesson 6.1 of Working with AI assistants, "Custom instructions: what to say once". A project is a workspace whose saved guidance applies only to the work inside it, covered in lesson 6.2 of the same course, "Projects: a workspace for each recurring job". A project is the better choice if you also use the assistant for work where your email voice is wrong, such as formal reports.
To test the guide, ask the assistant to draft an email you have already written, and compare its draft with yours. Wherever the draft still sounds wrong, ask the assistant what in the guide would have prevented it, and add a line to cover it. Two or three rounds usually give you a guide whose drafts you only need to adjust, not rewrite.
Collect your samples first. Then follow the steps above to build your guide, save it in custom instructions or a project, and keep testing it until the drafts need only small adjustments.
Produce a voice guide of under 200 words from at least five samples of your writing and save it where your assistant will use it.
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