A study for My Wine by Frederic de Lavenne de Choulot, The AI Pipe. 25 September 2026.

UK wine price questions: observed sources and one page to test

What the collection shows

Asked what a bottle of Penfolds Bin 389 2021 costs, Perplexity cited a comparison page whose lowest offer was a 2023 when we checked it. Below: that proof, and an acceptance test for your existing page prototype so that your pages never repeat that mismatch.

Around it, a sample of three AI search APIs (the OpenAI API, the Claude API, Perplexity Sonar; API answers, not the apps), 25 September 2026: 12 questions, four asked twice, 16 calls per API. Every API cited price comparison pages in part of its answers (OpenAI 5 of 11, Claude 8 of 16, Perplexity 11 of 16), alongside sellers' own pages. Of the 6 comparison pages cited for a question naming a vintage, 2 showed only that vintage. worldwinelist.com and mywine.dev: cited in 0 of 11, 0 of 16 and 0 of 16 answers, and not among the pages the searches returned (for Perplexity, the numbered source list it returns).

One answer, checked against its source

The front label is what the answer said. The back label is what the page it links to showed when we read it. Amounts are withheld on this page: a blank marks where the answer gave one.

Asked of Perplexity Sonar, 25 September 2026, 18:15 UK time

Penfolds
Bin 389 Cabernet Shiraz

Asked:

2021

75cl

“What does a bottle of Penfolds Bin 389 2021 cost in the UK?”

Price comparison data also shows the lowest tracked UK offer at £.[6]
Read the whole answer
A bottle of Penfolds Bin 389 2021 in the UK is typically around £ depending on the retailer.[2][3][4] Examples from current UK listings include £ per bottle at Fine Wine Direct, £ at HTFWines, and £ at Vinissimus.[4][3][2] Price comparison data also shows the lowest tracked UK offer at £.[6] If you want, I can also give you the cheapest UK retailer found in the results or the average price across the listings.

Source [6], a price comparison page

Penfolds Bin 389 Cabernet Shiraz, 75cl, 2021 (pricerunner.com)

Read at 18:20 UK time from its HTML, and again in a browser at 18:27. The answer was written at 18:15: this is what the page offered when we checked, not necessarily what the engine saw.

Linked offer when checked:

2023

8wines, Penfolds Bin 389 Cabernet Shiraz 2023; marked lowest price; shipping extra, 5 to 10 days.

The other offer: Majestic Wine, Penfolds 'Bin 389' Cabernet Sauvignon-Shiraz 2022/23; shipping extra, delivery next day. Excerpt of our copy of the page, time-stamped, amounts withheld.

  1. YesA link is attached to the statementMarker [6] follows the sentence and points to this page.
  2. YesThe linked page shows that amountIt is the 8wines offer, marked lowest price on the page (checked on our kept copy).
  3. NoVintageDoes not match the question: the page is titled 2021, the offer at that amount is a 2023.
  4. NoteDeliveryExtra on the source page; not specified in the answer.

Another page this answer cites, at Fine Wine Direct, is titled 'Bin 389 Cabernet Shiraz 2021/2023'. The finding is about this offer and this citation, not every merchant the answer names. No verdict on any price.

An acceptance test for your page prototype

Your brief says a public page prototype already works. I have not seen it. This is the test I would run on it first, built from the case above. It is a design rule, not an observation about your data, and it does not claim the page will be cited.

Test page
Penfolds Bin 389 Cabernet Shiraz 2021, 75cl, UK offers.
The rule

The lowest price on the page comes only from an offer that is available, in this bottle size, and confirmed as 2021. An offer labelled 2021/2023, or with no vintage, does not enter that minimum. With no eligible offer, the page says there is no confirmed offer for 2021, instead of showing another vintage.

Pass if
  • Each offer shows the vintage as the merchant's page states it; other vintages sit on their own page, linked.
  • Availability is shown on each offer, and an unavailable offer never sets the best price.
  • Delivery cost is shown when known; when unknown, the page says unknown, never free.
  • Membership, voucher, multi-buy or case-only terms sit on the offer they apply to, never in a headline price.
  • Each offer carries the time it was observed; the page carries when it was last updated.
  • The Fair Price Index keeps the definition mywine.dev gives: UK offers against the lowest price in the country of origin. Not a resale value, not a delivered price.
  • Product and Offer structured data say exactly what the page shows, and the page reads without an account or JavaScript.
Then measure
  1. Before publishing, ask the questions this page answers (the 2021 price, where to buy it, the fair price) several times on the same APIs and settings.
  2. Publish on one domain only, check the page is indexed.
  3. Ask the same questions several times again. Count whether the page is cited, and whether the vintage the answer gives is right. The other 11 questions stay a general control, not the result.
Other observationsCounts per API, the most cited sites, the comparison pages read, repeated questions.

Per API

12 questions; four asked twice; 16 calls per API. Complete answers only. An answer counts once per site type, whatever the number of links.

OpenAI APIClaude APIPerplexity Sonar
Answers collected161616
Complete answers111616
Without an answer500
Errors000
With at least one citation8 of 1116 of 1616 of 16
Citing a comparison page5 of 118 of 1611 of 16
Citing a seller's own page7 of 1113 of 1613 of 16
Citing an article or guide0 of 113 of 162 of 16
Citing worldwinelist.com0 of 110 of 160 of 16
Citing mywine.dev0 of 110 of 160 of 16

The sites cited most

Complete answers citing each site, per API.

trolley.co.uk (comparison)OpenAI 2, Claude 6, Perplexity 5
tesco.com (seller)OpenAI 2, Claude 1, Perplexity 8
finewinedirect.co.uk (seller)OpenAI 0, Claude 6, Perplexity 2
northandsouthwines.co.uk (seller)OpenAI 3, Claude 4, Perplexity 0
idealo.co.uk (comparison)OpenAI 0, Claude 0, Perplexity 5
laithwaites.co.uk (seller)OpenAI 0, Claude 2, Perplexity 3
pricerunner.com (comparison)OpenAI 0, Claude 0, Perplexity 5
costco.co.uk (seller)OpenAI 1, Claude 0, Perplexity 3
virginwines.co.uk (seller)OpenAI 2, Claude 0, Perplexity 2
countryclubuk.com (seller)OpenAI 1, Claude 2, Perplexity 0

Comparison pages read, wines sold by vintage

21 pages cited, 15 read from the copies we downloaded, 6 not readable by us (blocked or built by script). 3 of those read are Trolley brand averages over several products: they cannot state a vintage and are left out. Of the other 12: every offer states a vintage on 4, some offers on 5, none on 3. For the 6 cited on a question that named a vintage, that vintage alone was shown on 2, mixed with others on 2, absent on 1, and could not be told on 1. 3 of 12 say when prices were checked, which is a date, not a sign the prices are fresh.

Questions asked twice

Sites cited in both passes, out of all sites cited across the two.

How much is a bottle of Whispering Angel rosé in the UK at the moment?OpenAI 0 of 5; Claude 4 of 4; Perplexity 4 of 7
Where is Cloudy Bay Sauvignon Blanc 2025 cheapest in the UK right now?OpenAI 4 of 7; Claude 3 of 3; Perplexity 5 of 7
Where's the best deal on Veuve Clicquot Yellow Label champagne in the UK right now?OpenAI one pass without an answer; Claude 2 of 4; Perplexity 5 of 5
How much more does Laurent-Perrier La Cuvée cost in the UK than in France?OpenAI one pass without an answer; Claude 3 of 4; Perplexity 2 of 3

OpenAI answers without an answer

  • What does a bottle of Penfolds Bin 389 2021 cost in the UK? The whole answer is 'I'll check current UK prices for the 2021 vintage.' No search was run and no price was given.
  • Is Oyster Bay Sauvignon Blanc on offer anywhere in the UK this week? The answer announces a check twice ('I'll check current UK supermarket and wine-retailer offers...') and stops; no search, no offer named.
  • Where's the best deal on Veuve Clicquot Yellow Label champagne in the UK right now? The whole answer is 'I'll compare current UK prices including delivery where practical.' No search was run.
  • How much more does Laurent-Perrier La Cuvée cost in the UK than in France? The model asked a question back ('Roughly, or for a specific bottle size/retailer?') instead of answering.
  • What's the going rate for Dom Pérignon 2015 in the UK? The model announced a check, then wrote 'I can't verify live UK pricing without using the web' without running the search it had.
Your sites and the MCP connectorWhat public pages show without an account, checked on 25 September 2026.

worldwinelist.com

Examined without an account: robots.txt, sitemap.xml and 3 product pages (Laurent-Perrier La Cuvée 75cl, Moët & Chandon Impérial 75cl, Cloudy Bay Sauvignon Blanc 2020). Each page shows producer, cuvée, the vintages and sizes on file, country and appellation. None showed a price or a date in the HTML we received, and none carried structured data.

The sitemap lists 32,591 URLs: 5,430 product pages in each of five languages and 5,431 at the default address, six versions of each page; its lastmod field reads August or September 2023 (the sitemap's date field, not the age of your data). Several of the 12 wines have a page there, some for older vintages than the ones asked. robots.txt leaves product pages open to all crawlers and closes account paths: no obstacle identified in this limited check (firewall rules not tested). The home address https://worldwinelist.com/ redirects to http://worldwinelist.com/en/, which redirects back to https: one extra round trip, not a site served over http.

mywine.dev

The home page defines the Fair Price Index. The sitemap lists 3 URLs (home and two account pages), and robots.txt closes /mcp/documentation to crawlers. No page for a wine or a price was found on this domain in this check. Neither domain has an llms.txt; Google states that no AI-specific file is needed for its AI features, so that is not treated as a finding.

The MCP connector

mcp.mywine.dev asks for sign-in with a My Wine account (OAuth). I did not create an account, so I have not seen what it returns. Its public documentation says search_offers returns merchant listings with a direct link to buy. Access through the connector, for people who install it, is separate from being cited in an ordinary web answer. This study measures only the second and says nothing against the first.

MethodQuestions, API settings, counting rules, what was not measured, tests and archive.

The 12 questions

Written by us and selected for this test, not popular searches. Frozen before the first call; four asked twice. Each wine checked on UK merchant pages first. No question names My Wine, World Wine List or a site.

  1. 01How much is a bottle of Whispering Angel rosé in the UK at the moment? Asked twice.Caves d'Esclans, Whispering Angel, Côtes de Provence rosé; vintage: not stated by the asker; UK merchants list 2024 and 2025 on 25 Sep 2026 (Majestic shows '2024/25'); 75cl
  2. 02What does a bottle of Penfolds Bin 389 2021 cost in the UK?Penfolds, Bin 389 Cabernet Shiraz; vintage: 2021; 75cl
  3. 03Where is Cloudy Bay Sauvignon Blanc 2025 cheapest in the UK right now? Asked twice.Cloudy Bay, Sauvignon Blanc, Marlborough; vintage: 2025; 75cl
  4. 04Is Campo Viejo Rioja Reserva cheaper at Tesco or Sainsbury's?Campo Viejo, Rioja Reserva; vintage: not stated by the asker (supermarket listings carry no vintage in the title); 75cl
  5. 05Is Oyster Bay Sauvignon Blanc on offer anywhere in the UK this week?Oyster Bay, Marlborough Sauvignon Blanc; vintage: not stated by the asker; 75cl
  6. 06Where's the best deal on Veuve Clicquot Yellow Label champagne in the UK right now? Asked twice.Veuve Clicquot, Yellow Label Brut; vintage: NV; 75cl (the asker does not say)
  7. 07What's a fair price to pay for Moët & Chandon Impérial Brut in the UK?Moët & Chandon, Impérial Brut; vintage: NV; 75cl (the asker does not say)
  8. 08How much is a bottle of Château Margaux 2015 worth in the UK?Château Margaux, Premier Grand Cru Classé (grand vin); vintage: 2015; 75cl
  9. 09How much more does Laurent-Perrier La Cuvée cost in the UK than in France? Asked twice.Laurent-Perrier, La Cuvée Brut; vintage: NV; 75cl (the asker does not say)
  10. 10What's the going rate for Dom Pérignon 2015 in the UK?Dom Pérignon, Vintage Brut; vintage: 2015; 75cl (the asker does not say)
  11. 11Has Villa Maria Private Bin Sauvignon Blanc gone up in price in the UK over the past year?Villa Maria, Private Bin Marlborough Sauvignon Blanc; vintage: not stated by the asker; 75cl
  12. 12Which UK supermarket has the best-value bottle of Prosecco right now?No single wine: a category question.

API settings

  • OpenAI API: OpenAI Responses API, model chat-latest; web_search tool, tool choice left to the model, up to 4 searches; approximate location, country GB. No system prompt.
  • Claude API: Claude Messages API, model claude-sonnet-5; web_search_20250305 (direct search), up to 3 searches; approximate location, country GB. No system prompt.
  • Perplexity Sonar: Perplexity Sonar through OpenRouter, model perplexity/sonar; built-in web search; country GB sent in web_search_options; in a control test the same question returned the same sources with and without it, so through this route it had no visible effect. No system prompt.

First call started 25 September 2026, 18:15 UK time, last one finished at 18:19; 48 calls, 0 errors, 0 answers aimed at another country. Collection ran under a fixed spending cap with a check before every call.

What counts

  • Cited: a link the API attached to its answer (OpenAI url_citation annotations, Claude web_search_result_location citations, Perplexity numbered sources whose number appears in the text). A page the search returned but the answer does not cite is not a citation.
  • One site counts once per answer. worldwinelist.com and mywine.dev are kept apart; together they would count as one.
  • A name written without a link is recorded apart and never counts as a citation.
  • A failed call is an error, never an answer without citation. An answer where the model only said it would search, or asked a question back, is counted as without an answer. Both stay out of the denominators, and visible.
  • No rate across the three APIs: they are different products.

Not in this version

The consumer apps (ChatGPT, Claude, Perplexity) were not observed. Google AI Overviews: not measured, which is not zero. The Gemini API was left out because its Search grounding terms restrict reusing the links it returns.

Tests and archive

68 of 68 tests pass on the counting rules, using answers from this collection kept unchanged as fixtures: a repeated citation, a source only consulted, a name without a link, an answer without citation, a redirect, a search error inside a successful response. Every answer, with amounts withheld, is in the archive; readings in judgments.json, site types in domains.json, the panel in panel.json, the comparison page checks in comparison-pages.json.

Panel frozen at 25 September 2026, 18:14 UK time.