AI Product Detail Page Copy That Uses Only Your Spec Sheet

Give a model your product facts in one line and ask for a product page, and you get a headline like this: "Hot at 9 a.m., still hot at 3 p.m." Further down, a timetable: "3:00 p.m. Your last sips are still warm, close to the 6-hour mark." The spec sheet says 6 hours and nothing about clock times. A seller who publishes that is publishing a claim nobody tested.

The steps below use a made-up tumbler. Limit the input to a spec sheet, make every sentence cite a row, then check the numbers.

[1] First, see how a short prompt goes wrong.

Write a product detail page for a tumbler. 500 ml, stainless steel 304, keeps heat for 6 hours, weighs 320 g. For office workers who carry it to work every day.

$ claude -p --model claude-sonnet-5-5 --max-turns 1 --tools "" --setting-sources "" --strict-mcp-config < short.en.noans.txt > out.short.en.noanswer.txt

Lines from the 48-line result that are not in the input (… marks cuts):

**Hot at 9 a.m., still hot at 3 p.m.**It's enough for a large coffee or a couple of cups of tea, so you refill less often.It's a durable, widely used food-grade stainless steel. It's easy to rinse clean and doesn't hold on to the taste of yesterday's drink.- **3:00 p.m.** Your last sips are still warm, close to the 6-hour mark.1. Rinse with warm water and mild soap after each use.…

The clock times, the cup comparison, the "food-grade" label, the taste resistance and the care steps are all invented. The model did add a "Notes for you" list at the end that asks the seller to confirm the test conditions and the "food-grade" wording, but the sentences are already in the body.

[2] Put the spec sheet in a file with row numbers. Each sentence will cite one of them.

S1 | Capacity | 500 mlS2 | Body material | Stainless steel 304S3 | Heat retention | 6 hours (in-house test value)S4 | Weight | 320 gS5 | Cleaning | Not dishwasher safe, hand wash onlyS6 | Contents | 1 body, 1 lid

[3] Write the prompt. Spec and target go in tags so they stay apart from the instructions. The row-citation rule is the important part. Asking for a source per claim and dropping claims that have none comes from Anthropic's guide on reducing hallucinations.

Write draft sections of an online store product detail page using only the information in <spec>. Rules:- Use exactly these four sections: Pain point / Key benefits / Specs / Use and care. Write each section title as a `## ` heading.- Do not state anything that is not in <spec>. Do not invent ingredients, certifications, effects, numbers or comparisons (best, first in the industry, etc.).- Write one sentence per line and end each sentence with the spec row number, like `[S2]`. For several rows use `[S1][S3]`.- If a sentence has no supporting row, do not write it; where one is truly needed, end it with `[]` and nothing else.- A sentence containing a judgement such as "light" or "roomy" gets `[]` instead of `[S4]`, even if a number backs it. The spec sheet contains no judgements.- Do not repeat the same fact in two sections.- Copy numbers and units exactly as written in <spec>. Do not convert them.- No explanations or greetings outside the sections. <target>Office workers who carry it in a bag to work every day</target> <spec>

[4] Append the spec and the closing tag, then run it. The fixed sections make the output checkable line by line.

$ (cat head.en.txt spec.en.txt; echo "</spec>") > prompt.en.txt$ claude -p --model claude-sonnet-5-5 --max-turns 1 --tools "" --setting-sources "" --strict-mcp-config < prompt.en.txt > out.en.1.txt$ cat out.en.1.txt## Pain pointA bottle that goes into your work bag every day has to be easy to carry. [] ## Key benefitsHeat retention is 6 hours (in-house test value). [S3]At 320 g, it is light enough to carry in a bag every day. [] ## SpecsCapacity is 500 ml. [S1]The body material is Stainless steel 304. [S2]The package contains 1 body, 1 lid. [S6] ## Use and careIt is not dishwasher safe, so hand wash only. [S5]

A second run (out.en.2.txt) used the same numbers and tags. It listed the weight as its own [S4] line under Specs instead of folding it into a "light" sentence, and its pain-point line said only "A bottle you carry in your bag to work every day has to suit that routine. []".

[5] Write the checker. It pulls every number with its unit from the draft and looks for it in the spec values, then checks that each sentence ends in [S#] or []. Heading lines are skipped for the number check.

#!/usr/bin/env python3# usage: check.py spec.txt draft.txtimport re, sysNUM = re.compile(r"(\d+(?:\.\d+)?)\s*(ml|kg|g|시간|개|℃|%|시|분|일|hours?|)", re.I)pairs = lambda t: {(n, u.lower()) for n, u in NUM.findall(t)}spec = open(sys.argv[1], encoding="utf-8").read()allowed = pairs("\n".join(l.split("|", 2)[2] for l in spec.splitlines() if l.count("|") >= 2))draft = open(sys.argv[2], encoding="utf-8").read()body = "\n".join(l for l in re.sub(r"\[S\d+\]", "", draft).splitlines() if not l.lstrip().startswith("#"))bad = sorted(p for p in pairs(body) if p not in allowed)print("not in spec :", bad or "none")lines = [l.strip() for l in draft.splitlines() if l.strip() and not l.lstrip().startswith(("#", "---"))]noref = [l for l in lines if not re.search(r"(\[S\d+\])+$|\[\]$", l)]for l in noref: print("NO REF      :", l[:60])print(f"{len(lines)} lines, {len(noref)} without a reference, {len(bad)} numbers not in spec")sys.exit(1 if bad or noref else 0)

[6] Check both results.

$ python3 -I check.py spec.en.txt out.en.1.txt; echo "exit $?"not in spec : none7 lines, 0 without a reference, 0 numbers not in specexit 0$ python3 -I check.py spec.en.txt out.short.en.noanswer.txt | grep -v '^NO REF'; echo "exit ${PIPESTATUS[0]}"not in spec : [('00', ''), ('12', ''), ('2', ''), ('3', ''), ('30', ''), ('6', ''), ('7', ''), ('9', '')]48 lines, 48 without a reference, 8 numbers not in specexit 1

Real problems in the short result are the clock times: 7, 9, 12, 3 and the 30 and 00 after the colons come from "7:30 a.m.", "9:00 a.m.", "12:30 p.m.", "3:00 p.m." and "7:00 p.m.". 2 and 3 also come from the numbered care steps, which is noise. 6 is a false positive: the draft says "6-hour" and the checker only reads "6 hours" as a unit pair. The checker cannot catch an invented claim that has no number, such as "doesn't hold on to the taste of yesterday's drink".

[7] Two places still need a human read after a pass.

• A tag is not proof. The checker only sees that a tag is present. A sentence calling the bottle "light" tagged [S4] would pass, though S4 is only 320 g and "light" is a judgement. That is why the prompt has the judgement rule, and in out.en.1.txt it worked: "At 320 g, it is light enough to carry…" got [].
• [] means "decide before publishing", not "safe to delete". In out.en.1.txt that "light" sentence is the only place the 320 g appears. Strip every [] line and the weight is gone from the page. The pain-point lines are [] too and say almost nothing.

Do not use this as a substitute for the seller's own check. Certifications, materials and test conditions that are missing from the sheet have to come from you, and wording such as "in-house test value" is something to confirm separately.