Make AI Hit Your Length Limit Almost Every Single Time

The Concept: The AI as Your Precision Copy Fitter

A few weeks ago I was talking with Rachel, a senior content manager.

She pulled up her laptop and showed me an email she’d just gotten from her boss. It was short: “Rachel, can we make these updates shorter? I don’t have time to read novels.”

“This is the third time he’s said this,” Rachel said, frustrated.

“Look at what I sent him.”

She showed me the email she sent. It was beautifully written, comprehensive, detailed, and… about 400 words long.

“I want to make sure he has all the context,” Rachel explained. “All the metrics, the insights, the recommendations. I spend hours on these.”

“How long does your CEO have to read your emails?” I asked.

“He reads them between meetings, so probably like 30 seconds max.”

“And how long does it take to read 400 words?”

Rachel did the math. “About… two minutes.”

“So you’re writing for someone who doesn’t exist: a CEO with two minutes to spare.”

But then Rachel showed me something else. It wasn’t just the executive emails. She opened her social media drafts. LinkedIn posts getting cut off with “see more,” Instagram captions that were novels, Twitter threads that nobody finished reading. Her email subject lines were getting truncated. Her product descriptions were too long for mobile screens.

“I use AI for all of this,” she said, “but it always writes too much. I spend forever cutting things down to fit.”

“What if I told you that you could get AI to hit your length limits almost perfectly every single time?” I asked.

“That’s impossible. I’ve tried asking for ‘short’ or ‘brief’ and it never works.”

“You’re not being specific enough.” I said, and then proceeded to teach her the correct way to make the AI hit a certain length limit.

The technique is beautifully simple: Instead of asking AI to write something “brief” or “short” (which means nothing specific), you give it exact constraints such as word counts, sentence counts, or paragraph structures.

Let me show you exactly how Rachel transformed not just her executive emails, but every piece of content she creates.

How It Works: A “Toolbox” of Length Commands

You can direct AI’s output length with several types of clear, specific commands. I prefer these over asking AI to make something “long” or “short” because those commands aren’t relative to anything. What’s short for one person might be long for another.

1. By Word Count (Good for body copy, articles, and descriptions)

One of the most common ways to limit an AI’s output is by giving it a word count limit right in the prompt itself:

AI Prompt

[CONTENT MARKETING PERFORMANCE THIS WEEK]:
– Published 5 blog posts, 2 whitepapers
– Organic traffic up 15% week-over-week
– Email newsletter reached 45% open rate (industry average: 22%)
– Generated 127 MQLs (target was 100)
– Top performing content: “AI in B2B Sales” blog post (10K views)
– Social media engagement up 30%

[DIRECTIONS]:
I am Rachel, a senior content manager. Write an email to my boss about our content marketing performance this week. The email should use approximately 50 words.

[EMAIL]:

AI Response

Subject: Weekly Content Performance Update

Hi [Boss Name],

Excellent week for content marketing! Published 7 pieces (5 blogs, 2 whitepapers), driving 15% traffic increase and 127 MQLs (27% above target). Newsletter hit 45% open rate vs. 22% industry average. “AI in B2B Sales” post reached 10K views. Social engagement up 30%.

Best,
Rachel

The AI’s response is 43 words (if we’re just considering the body paragraph), which is pretty close to the 50 word limit. Without the word count limit, the AI wrote 168 words in one of my tests. So that’s a big difference!

Now you’re probably wondering why the AI didn’t get it exact at 50 words. Well, after thousands of hours of prompting, I’ve found the AI rarely gets it exact. So you’ll just have to settle for close enough.

2. By Sentence Count (Great for summaries, headlines, and impactful statements)

You can also limit the output by sentence count:

AI Prompt

AI Response

Subject: Weekly Content Marketing Performance Update

Hi [Boss’s name],

I’m pleased to report that our content marketing efforts exceeded expectations this week, with our team publishing 7 pieces of content that drove a 15% increase in organic traffic and generated 127 MQLs, which was 27% above our target of 100. Our email newsletter significantly outperformed industry benchmarks with a 45% open rate compared to the 22% average, while our “AI in B2B Sales” blog post became our top performer with 10K views. Additionally, we saw strong engagement across social channels with a 30% uptick, indicating our content strategy is resonating well with our target audience.

Best regards,
Rachel

The AI hit our goal of three sentences, but something interesting happened!

Do you see it?

Let’s compare the word count in both examples we did:

In the first example where I gave the AI a word count and no sentence count, the word count was 43 words and three sentences.
In this example where I gave the AI a sentence count and no word count, the word count was 96 words and three sentences.

Why are the sentences in this example so much longer?

The answer’s strange, and it’s a unique trait of large language AI models (LLMs).

It’s because the AI loves writing long sentences.

When I limited the word count, I got shorter sentences. But when I asked for three sentences without a word limit, the AI got drunk on long sentences and went wild!

Just keep this in mind when you’re using a sentence limit versus a word limit.

3. By Paragraph Count (Ideal for emails, reports, and blog post sections)

Another way you can limit your output is by paragraph count:

AI Prompt

AI Response

Subject: Weekly Content Marketing Performance – Strong Results Across All Metrics

Hi [Boss’s Name],

I wanted to share this week’s content marketing results, which exceeded our targets across multiple channels. We published 5 blog posts and 2 whitepapers, driving a 15% increase in organic traffic week-over-week. Our email newsletter performed exceptionally well with a 45% open rate—more than double the industry average of 22%. Most importantly, we generated 127 MQLs, surpassing our target of 100 by 27%.

The standout performer was our “AI in B2B Sales” blog post, which garnered 10K views and likely contributed to our strong lead generation numbers. Social media engagement also jumped 30%, indicating our content is resonating well with our audience across platforms. The combination of quality content output and strong engagement metrics suggests our current content strategy is effectively driving both awareness and conversions.

Best regards,
Rachel

In this example, I got exactly what I wanted: two paragraphs.

Just like in the sentence limit example, the sentences get pretty long when you’re limiting output by paragraphs. So keep that in mind when you’re trying this approach.

Additional AI Length Limit Tips

Now, before you run off and tell the AI to limit its output, there are a few more things you need to know based on what I’ve learned over the years.

1. The Wrong Type of Length Limit May Harm the AI’s Creativity

I’ve noticed something interesting: when you ask AI to create something it knows well (like an email, LinkedIn post, Facebook post, or X post), its creativity can actually drop if you use the wrong type of limit in your prompt.

Let me show you an example:

AI Prompt

Product: Noise Gobblers. Active noise cancellation technology blocking up to 95% ambient sound. Custom-tuned 40mm dynamic drivers. 30-hour battery life (ANC on) / 40-hour battery life (ANC off). 15-minute quick charge for 3 hours playback. Premium memory foam ear cushions. Bluetooth 5.2 with multi-device pairing. Built-in microphones with voice clarity enhancement. Touch controls for music, calls, voice assistant. Foldable design with carrying case. Frequency response: 20Hz – 20kHz. Impedance: 32 ohms. Weight: 250g. USB-C fast charging. 3.5mm wired audio cable included. Available in matte black, silver, midnight blue. Compatible with all Bluetooth devices. 2-year manufacturer warranty. 30-day satisfaction guarantee.

Write a Facebook post about our product and the black-friday sale we are having for 50% off to the first 100 customers.

AI Response

🔥 BLACK FRIDAY EXCLUSIVE: 50% OFF Noise Gobblers Headphones! 🔥

Block out 95% of ambient noise with our premium active noise cancellation technology. Experience crystal-clear audio through custom-tuned 40mm dynamic drivers with an incredible 30-hour battery life.

✨ What makes Noise Gobblers special:
🎧 95% noise cancellation
🔋 30-40 hours battery life
⚡ 15-minute quick charge = 3 hours playback
☁️ Premium memory foam cushions
📱 Bluetooth 5.2 with multi-device pairing
🎙️ Enhanced voice clarity for calls
👆 Intuitive touch controls
🎒 Foldable design with carrying case

Available in matte black, silver, and midnight blue.
⏰ LIMITED TIME: First 100 customers get 50% OFF!
📦 Free shipping included
🛡️ 2-year warranty + 30-day satisfaction guarantee

Don’t miss out on the best deal of the year! Your ears (and wallet) will thank you.
🛒 Shop now before they’re gone!

BlackFriday #NoiseGobblers #HeadphonesDeals #ActiveNoiseCancellation #LimitedOffer

The output from that response without length limits looks good. It’s got all the stuff you’d expect in a typical Facebook post. You know, a headline that grabs attention, an intro paragraph, a list packed with emojis, some FOMO language, and hashtags at the end.

Now, if you want to limit the length of a Facebook post, the right type of limit would be a word limit.

Here an example of limiting it to 100 words:

AI Prompt

AI Response

🎧 BLACK FRIDAY EXCLUSIVE: 50% OFF Noise Gobblers! 🎧

Block 95% of ambient noise with our premium active noise cancellation headphones. Features include:
– 40-hour battery life
– Custom 40mm drivers
– 15-min quick charge = 3 hours playback
– Bluetooth 5.2 multi-device pairing
– Premium memory foam cushions
– Touch controls & voice assistant

Available in matte black, silver, and midnight blue. Includes carrying case, USB-C charging, and 3.5mm cable.

⚡ FIRST 100 CUSTOMERS ONLY – 50% OFF! ⚡
2-year warranty | 30-day satisfaction guarantee

Don’t miss out! Limited stock available.

#BlackFriday #NoiseGobblers #Headphones #Deal

When you limit your Facebook prompt by a certain number of words, the result still looks like a Facebook post.

But what happens when you limit it to a certain number of paragraphs? In that case, the output breaks and doesn’t look like a Facebook post. It sucks pretty hard, honestly.

Here is the output when we limit it to two paragraphs:

AI Prompt

AI Response

🔥 BLACK FRIDAY EXCLUSIVE: Noise Gobblers Headphones 50% OFF! 🔥 Experience premium audio like never before with our cutting-edge active noise cancellation technology that blocks up to 95% of ambient sound. These aren’t just headphones – they’re your personal sound sanctuary featuring custom-tuned 40mm dynamic drivers, an incredible 30-hour battery life with ANC on, and lightning-fast 15-minute quick charging that gives you 3 hours of playback. The premium memory foam ear cushions and foldable design make them perfect for travel, work, or relaxation.

⚡ LIMITED TIME: First 100 customers only! Don’t miss this chance to upgrade your audio experience with Bluetooth 5.2 multi-device pairing, crystal-clear built-in microphones, intuitive touch controls, and your choice of matte black, silver, or midnight blue. With a 2-year warranty, 30-day satisfaction guarantee, and both wireless and wired connectivity options, these premium headphones deliver professional-grade sound at an unbeatable price. Comment “GOBBLERS” below and we’ll send you the exclusive link – but hurry, this deal disappears when we hit 100 orders! 🎧✨

Ouch. That doesn’t look like a Facebook post at all.

So here’s what I’d recommend: test the prompt without a limit first to establish a baseline. Then try different limit types (like word limits, sentence limits, paragraph limits) and see which one keeps the original formatting best.

And again, this only becomes an issue when you’re asking the AI to make a “thing” that it actually knows. You know, something it’s been trained on and can try to copy.

2. Your Mileage will Vary by Model

I think many of you already know this, but if you don’t, here’s something critically important: the quality of your output and the AI’s ability to follow your length limits depends entirely on which model you pick.

So if you’re not getting great results with your usual model, switch it up and try a different one. You could also switch providers. Maybe a prompt with a length limit that works great in Anthropic’s Claude Sonnet 4 chat doesn’t work well in OpenAI’s ChatGPT using GPT-5.

Let’s look at an example of this in action.

Remember that Facebook prompt for the Noise Gobbler headphones that we did above? The one were we limited the output to 100 words? Here’s the result again from Anthropic’s Claude Sonnet 4 to jog your memory:

AI Prompt

AI Response

The output still looks like a Facebook post, and it’s within our word limit.

But what happens if we run this same prompt in OpenAI’s ChatGPT using GPT-5?

Let’s find out:

AI Response

Black Friday Alert! Meet Noise Gobblers—our premium ANC headphones blocking up to 95% ambient sound. Enjoy 30-hour battery life (ANC on), custom-tuned 40mm drivers, Bluetooth 5.2 with multi-device pairing, and plush memory foam comfort. Quick charge: 15 minutes = 3 hours playback. Touch controls, clear-call mics, foldable design, USB-C, and a 3.5mm cable included. Available in matte black, silver, and midnight blue. 2-year warranty + 30-day satisfaction guarantee.

Black Friday Deal: 50% OFF for the first 100 customers. Don’t miss out—grab yours now! Compatible with all Bluetooth devices. #NoiseGobblers #BlackFriday #ANC #Headphones #Deal

Ouch.

Yeah, that looks pretty rough for a Facebook post.

So it just goes to show you that not only does your prompt matter, but the AI model you choose matters too.

The takeaway is to test everything!

Test your prompts.

Test different models with your prompt.

Testing everything is how you get higher quality results in the long run.