Most brand voice guides read like a wish. They talk about tone in the abstract. They list adjectives. Then a writer ignores them, because none of it turns into a decision at the sentence level. An agent will do the same thing. If a rule cannot be checked against the draft, it will not change the draft.
The rules that actually work are small, specific and testable. A banned word list is testable. A sentence length ceiling is testable. "Sound confident but human" is not. This post walks through the five kinds of rule worth writing down before an agent writes for you. It shows what each one does to the output. And it ends with a starter ruleset you can paste into RankMill or any similar setup.
What a writing rule needs to do
A useful rule has three properties. It applies to a sentence you can point at. A reader can tell if the draft broke it. And it changes what the agent would otherwise write.
"Be professional" fails all three. "Never use an em dash" passes all three. The gap between those two is where the work is.
Think of the ruleset as a filter that runs on every draft the writer produces. Each rule you add is a small check the writer has to satisfy. The tighter the filter, the more the drafts start to sound like you and not like the model's default voice.
The five rules worth writing down
Banned words and phrases
The fastest win. Every model has tics. "Delve into", "in today's fast-paced world", "unlock the power of", "it is important to note", "in conclusion". They sound like nothing, and they mark a post as AI-written faster than any watermark.
Write down the ones you never want to see. Add "leverage" as a verb if you hate it. Add "seamless" if it makes you flinch. Add the phrase your competitors overuse. The list does not have to be short. A writer agent can hold twenty rules in mind without breaking a sweat.
A sentence length ceiling
Long sentences are where models go to hide. A single 45-word sentence can carry three half-thoughts and one hedge, and no reader will finish it.
Set a ceiling of twenty to twenty-five words per sentence. Add a rule that says "break a long one in two". This shifts the rhythm of a draft more than any other single instruction. It also forces the writer to say what it means, because a long sentence is often a short one wearing padding.
The jargon you allow, and the jargon you do not
Every field has words the model will reach for by default that your audience does not use. And every field has words your audience does use that a general model will avoid because they sound too niche.
Write down both lists. If your readers say "post" and not "article", say so. If they say "run" and not "execution", say so. If you never want to see "solutions" as a noun, say so. If your product has a name, spell it exactly the way it should appear, capitalisation and all.
This is the rule that most reliably makes an agent sound like it knows your industry. The model already knows the words. It just needs to know which ones are yours.
Point of view
Second person or third person. Singular "you" or plural "we". This is a one-line rule that shows up in every sentence.
Second person reads as direct and helpful. Third person reads as neutral and reference-like. Neither is right in the abstract. What matters is that you pick one and the writer sticks to it. A post that drifts between second and third person reads as though two people wrote it.
How to cite and link
Do you want inline links, or a references section at the end. Do you want the writer to name the source in the sentence, or just link the phrase. Do you allow claims that do not have a source at all.
Most teams do not think about this until a post ships with three links to a competitor's blog. Write it down first. A rule like "link only to primary sources or the official docs of the tool being discussed" removes a whole class of embarrassing drafts.
Before and after
Here is the kind of paragraph a writer agent turns out with no rules other than "write about setting up an AI content workflow":
In today's fast-paced digital landscape, it is important to note that leveraging AI-powered content solutions can unlock tremendous value for organizations looking to scale their content operations. Companies must delve into the various platforms available and select the one that best aligns with their unique business objectives.
Two sentences, forty-seven words, and it says almost nothing. Most of the tics listed above are in there, and so are "leverage" and "solutions".
Now the same brief, rewritten to a small ruleset. No em dashes. No AI clichés. Twenty-word sentence ceiling. Second person. Use "post" not "content". British spelling. No hype.
Setting up an AI writing tool takes an afternoon. You point it at your site, you write down the rules you want every post to follow, and you approve the first topic it suggests. The rest is checking the drafts.
Three sentences, forty words. Same subject, but a reader can act on it.
The change is not the model. It is the filter. The second draft is what the first would have been, if the rules had told it to stop reaching for padding.
Where rules bite hardest
Some rules change one sentence in ten. Others change every sentence. Roughly, in order of how much they shift a draft:
- Banned words and phrases. Change many sentences across a full backlog.
- Sentence length ceiling. Changes the shape of every paragraph.
- Point of view. Changes the first word of most sentences.
- Jargon rules. Change the nouns and verbs. Slower but permanent.
- Citation style. Changes a paragraph here and there, but saves the occasional rewrite.
If you only have time to write down one thing, write down the banned phrases. If you have an hour, add the other four.
A starter ruleset
Edit this for your business, then paste it in, one rule per line. In RankMill, writing rules go in on the create-project form, under "Competitors and writing rules", and they cannot be changed once the project exists, so do the editing before you create it.
Never use an em dash. Use a comma, a colon or a second sentence.
Never use the phrases "delve into", "in today's fast-paced world", "unlock the power of", "it is important to note", or "in conclusion".
Never use "leverage" as a verb. Use "use".
Never use "solutions" as a noun for a product or service.
Keep sentences under 25 words. Break a long one in two.
Write in the second person. Address the reader as "you".
Use British spelling: colour, behaviour, organise, recognise.
Headings are sentence case, and they say what the section is about.
Do not open a post with a general statement about the industry. Start with the useful part.
Do not invent numbers, prices, dates, customer names or statistics. If a fact is not given to you, write around it.
Link only to primary sources or to the official documentation of a tool you mention.
Do not use emoji in body copy, and do not use exclamation marks.
Twelve lines. It will not turn a bad topic into a good post, but it will stop a good topic from arriving as a bad draft. Adjust the banned phrases to the ones that grate on you. Swap the spelling to American if that is what your audience reads. Add the words your industry uses that a general model would not.
Making the ruleset yours
Read your own last three posts before you finalise the list. The rules you actually want are the ones you were already applying by hand. If you rewrote every "leverage" to "use", write that down. If you kept breaking up long sentences, add the ceiling. If you kept swapping "utilise" for "use", ban "utilise".
Rules earn their place by catching something. Every so often, read a fresh draft and ask what you would have edited. If the answer is nothing the current rules would catch, you have found a rule that is missing. If a rule has not fired in a month, it is not pulling its weight.
In RankMill that review lands in two places, because a project's writing rules are fixed once it is created. The website profile, which describes how the business sounds and which every agent reads, stays editable, so a correction to voice or vocabulary can go there. And a post started from your own idea takes extra rules for that one post on top of the project's.
The point of writing rules down is not to constrain the writer. It is to stop having the same argument with every draft. A good ruleset is the argument you already had, written down once, so the next post starts where the last one ended.