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User in the loop

Find a winning headline without the internal debate

Thirty lines of copy, scored against a model of your users, to find out which part of the product is worth leading with.

This lesson picks the launch headline for an AI tool that chases late invoices for a small business. Thirty work-in-progress lines of copy go in, scored one at a time against a model of 400 UK SMEs. The top six sit within four points of each other, so a second simulation asks what those six make people think the product is, and the line with the highest click intent is the one that makes 59% expect a debt collection agency. A third tests that line with different subtexts underneath it. The page goes out with the winning headline and the subtext that says what the product does.

What you'd normally do

Pick it in a meeting, or run an A/B test after launch. A meeting settles it in an hour on the opinions of the people in the room. An A/B test needs about three weeks of traffic, and it only compares the two lines somebody already chose.

What you bring

One description of the product, and thirty lines to test against it. The thirty here came from Claude, in the same thread the feature had been specified in, so it already knew what the product was.

The description is the part that matters. It goes in once and stays fixed, so every line is read against the same product and the round tests the copy rather than the concept underneath it.

For a round like this you can bring any set of short text where only one of them can go live:

  • Headlines for a landing page
  • Subject lines for a launch email
  • An app store title and its description
  • The sentence you use when someone asks what you do
Staying in control See every late invoice in 60 seconds. Send nothing until you say so. It never emails a client you've excluded. No exceptions. Nothing is ever sent until you press send. Watch it work before you let it touch anything. It reads your books. It never touches them. It drafts the awkward email. You press send. You approve every email, or nothing goes out at all. Read-only until you say otherwise. The money owed You did the work. Now get paid for it. Money in. Evenings back. Stop being the person who chases money you're already owed. What would you do with the money your clients still owe you? Get paid for the job you finished in March. Your oldest unpaid invoice is older than you think. Your cash flow problem is mostly a chasing problem. The chasing work Chasing money is work. Stop doing it unpaid. Every overdue invoice on one screen. One tap to chase the lot. The follow-up you keep putting off is already drafted. Ten chasers drafted, approved in one tap. Stop rewriting the same 'just following up' email. From 'must chase that up' to 'that's been paid'. The reminder goes out on day 3, not when you finally get round to it. Late payers don't need your evenings. They need a nudge on day 3 and a firm word on day 10. The relationship Chase the invoice without becoming the nag. Firm with the money, gentle with the relationship. What it costs Pay 5% of what gets recovered. Pay nothing until it does. No monthly fee. No fee at all until an invoice gets paid. Proof it works A plumber in Leeds got £4,200 of late invoices paid. Your trade next. Connect your accounts, see what you're owed, decide what happens next. An activity log your accountant can actually read. Staying in control See every late invoice in 60 seconds. Send nothing until you say so. It never emails a client you've excluded. No exceptions. Nothing is ever sent until you press send. Watch it work before you let it touch anything. It reads your books. It never touches them. It drafts the awkward email. You press send. You approve every email, or nothing goes out at all. Read-only until you say otherwise. The money owed You did the work. Now get paid for it. Money in. Evenings back. Stop being the person who chases money you're already owed. What would you do with the money your clients still owe you? Get paid for the job you finished in March. Your oldest unpaid invoice is older than you think. Your cash flow problem is mostly a chasing problem. The chasing work Chasing money is work. Stop doing it unpaid. Every overdue invoice on one screen. One tap to chase the lot. The follow-up you keep putting off is already drafted. Ten chasers drafted, approved in one tap. Stop rewriting the same 'just following up' email. From 'must chase that up' to 'that's been paid'. The reminder goes out on day 3, not when you finally get round to it. Late payers don't need your evenings. They need a nudge on day 3 and a firm word on day 10. The relationship Chase the invoice without becoming the nag. Firm with the money, gentle with the relationship. What it costs Pay 5% of what gets recovered. Pay nothing until it does. No monthly fee. No fee at all until an invoice gets paid. Proof it works A plumber in Leeds got £4,200 of late invoices paid. Your trade next. Connect your accounts, see what you're owed, decide what happens next. An activity log your accountant can actually read.
The thirty lines going in, grouped by which part of the product each one leads with.

What comes back

Every line was shown against the same description of the product, as "a tool that automatically drafts chasing emails for your overdue invoices", and each respondent was asked how much the line made them want to learn more. All thirty ran as a single simulation.

While it was still running, the agent said what the scores were not going to settle:

When they land, the top few will be close, so the natural next step is a smaller round putting just those leaders against each other on clarity and standout.

Thirty lines scored one at a time You did the work. Now get paid for it. 71% Pay 5% of what gets recovered. Pay nothing… 70% Money in. Evenings back. 69% No monthly fee. No fee at all until an invo… 67% Stop being the person who chases money you'… 67% What would you do with the money your clien… 67% A plumber in Leeds got £4,200 of late invoi… 66% Get paid for the job you finished in March. 65% Chasing money is work. Stop doing it unpaid. 65% See every late invoice in 60 seconds. Send… 63% Every overdue invoice on one screen. One ta… 61% It never emails a client you've excluded. N… 57% The follow-up you keep putting off is alrea… 57% Ten chasers drafted, approved in one tap. 56% Nothing is ever sent until you press send. 55% Stop rewriting the same 'just following up'… 55% Your oldest unpaid invoice is older than yo… 55% From 'must chase that up' to 'that's been p… 55% Watch it work before you let it touch anyth… 53% Connect your accounts, see what you're owed… 53% It reads your books. It never touches them. 52% It drafts the awkward email. You press send. 51% The reminder goes out on day 3, not when yo… 51% Late payers don't need your evenings. They… 51% Your cash flow problem is mostly a chasing… 51% Chase the invoice without becoming the nag. 50% You approve every email, or nothing goes ou… 50% An activity log your accountant can actuall… 45% Firm with the money, gentle with the relati… 44% Read-only until you say otherwise. 42% Round 2 what people think it is Thirty lines scored one at a time You did the work. Now get paid fo… 71% Pay 5% of what gets recovered. Pa… 70% Money in. Evenings back. 69% No monthly fee. No fee at all unt… 67% Stop being the person who chases… 67% What would you do with the money… 67% A plumber in Leeds got £4,200 of… 66% Get paid for the job you finished… 65% Chasing money is work. Stop doing… 65% See every late invoice in 60 seco… 63% Every overdue invoice on one scre… 61% It never emails a client you've e… 57% The follow-up you keep putting of… 57% Ten chasers drafted, approved in… 56% Nothing is ever sent until you pr… 55% Stop rewriting the same 'just fol… 55% Your oldest unpaid invoice is old… 55% From 'must chase that up' to 'tha… 55% Watch it work before you let it t… 53% Connect your accounts, see what y… 53% It reads your books. It never tou… 52% It drafts the awkward email. You… 51% The reminder goes out on day 3, n… 51% Late payers don't need your eveni… 51% Your cash flow problem is mostly… 51% Chase the invoice without becomin… 50% You approve every email, or nothi… 50% An activity log your accountant c… 45% Firm with the money, gentle with… 44% Read-only until you say otherwise. 42% Round 2 the top six go through
All thirty ranked by score, with the six that went into the second simulation marked. Longer lines are shortened here to fit.

Six came back close enough together that the scores could not separate them, so those six went into a second simulation. That one asked four more things: whether the line would make someone click, whether it looked like a product for a business like theirs, whether they believed the claim it made, and what they expected the product to be before they knew anything about it.

Appeal ↑ Would click ↑ Right fit ↑ Not credible ↓ Wrong product ↓ You did the work. Now get paid for it. 71% 80% 65% 35% 59% Pay 5% of what gets recovered. Pay noth… 70% 71% 51% 76% — Money in. Evenings back. 69% 77% 57% 68% 32% No monthly fee. No fee at all until an… 67% 78% 56% 63% — Stop being the person who chases money… 67% 74% 49% 57% 43% What would you do with the money your c… 67% 66% 45% 74% 48% You did the work. Now get paid for it. Appeal ↑ 71% Would click ↑ 80% Right fit ↑ 65% Not credible ↓ 35% Wrong product ↓ 59% Pay 5% of what gets recovered. Pay nothing until it does. Appeal ↑ 70% Would click ↑ 71% Right fit ↑ 51% Not credible ↓ 76% Wrong product ↓ — Money in. Evenings back. Appeal ↑ 69% Would click ↑ 77% Right fit ↑ 57% Not credible ↓ 68% Wrong product ↓ 32% No monthly fee. No fee at all until an invoice gets paid. Appeal ↑ 67% Would click ↑ 78% Right fit ↑ 56% Not credible ↓ 63% Wrong product ↓ — Stop being the person who chases money you're already owed. Appeal ↑ 67% Would click ↑ 74% Right fit ↑ 49% Not credible ↓ 57% Wrong product ↓ 43% What would you do with the money your clients still owe you? Appeal ↑ 67% Would click ↑ 66% Right fit ↑ 45% Not credible ↓ 74% Wrong product ↓ 48%
The six leaders scored across every question the second simulation asked. The two pricing lines were not asked what product people pictured, since the question was about the claim rather than the category.

One line is the most appealing, the most clicked, the best fit and the most believed, but it is also the one people are most likely to take for a debt collection agency, a lender or a factoring service. That is the only thing left to fix, so the third simulation stops comparing headlines and starts testing what to put underneath the one that won.

Hero and subtext combinations Would click You did the work. Now get paid for it. A plumber in Leeds recovered £4,200 of late invoices in 10 days. 80% You did the work. Now get paid for it. No monthly fee. No fee at all until an invoice gets paid. 79% You did the work. Now get paid for it. Nothing under it. 77% You did the work. Now get paid for it. Automated email reminders for every overdue invoice, drafted for your approval. Nothing sends until you press send. 75% Hero and subtext combinations You did the work. Now get paid for it. A plumber in Leeds recovered £4,200 of late invoices in 10 days. 80% would click You did the work. Now get paid for it. No monthly fee. No fee at all until an invoice gets paid. 79% would click You did the work. Now get paid for it. Nothing under it. 77% would click You did the work. Now get paid for it. Automated email reminders for every overdue invoice, drafted for your approval. Nothing sends until you press send. 75% would click
Each hero and subtext pair, and how many said they would be very likely to click it. Two further versions reworded the hero line itself and are left out here.

The two that score highest are a customer story and a price, and neither of them says what the product is. The line describing the mechanism comes last of the four, five points behind the top, and it is the only one that answers the question the second simulation raised.

The synthesis naming the winning headline, with the click and credibility evidence behind it
The synthesis names the winner and says what is wrong with the two lines that beat it on clicks. Run against UK SMEs. A model of your own users would answer differently.

What you changed because of it

You did the work. Now get paid for it.
A plumber in Leeds recovered £4,200 of late invoices in 10 days.

You did the work. Now get paid for it.
Automated email reminders for every overdue invoice, drafted for your approval. Nothing sends until you press send.

The page goes out with the line that explains the product. The simulation was asked whether people would click, not whether they would understand what they were clicking, and five points of click is worth giving up if the clicks it loses come from people looking for a debt collection agency.

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