How ATLS finds every listing
When you open a card on ATLS, you should see every listing for it and the best price. Here's how a listing gets from a marketplace onto that card, and how we check we didn't miss one.
Every listing, and the best price
A background job works card by card through the cards people view, save and follow, cards worth $25 or more, and cards we know exist graded. For each card it searches the marketplaces, reads what comes back, and decides which listings really are that card.
No one has to ask for this. It runs in the background around the clock, so a card's listings are usually waiting when you open it.
Three stages
Every listing passes through three stages: search (what we ask the marketplace), read (how many results we look at) and judge (is this title this card?).
A miss at any one of them hides a listing. If the search never asks the right way, if we stop reading too early, or if we judge a real match wrong, you won't see it. The rest of this page takes the stages one at a time.
Ask the way sellers write it
Sellers type card numbers however they like. The same card shows up as 002/132 in one title and 2/132 in the next. Some write #025 with the rarity, like SSP, further along.
So we search for each card in the ways sellers actually write it, not only the way the catalog does.
A second, broader search
Important cards get a second search that casts a wider net, for example Wing Gundam Zero GD05. It brings back more listings, so what comes back from it is judged more strictly (more on that in stage 3).
Cards with no number
Some cards don't have a number at all, like One Piece DON!! cards. Those are searched by name plus the words that mark the printing.
Learning better wordings
When we find a listing we missed, the system asks why. Often the seller wrote the card a way we didn't search for, so it proposes a new wording.
A proposal isn't trusted on its own. We run it as a live search first, and the wording is adopted only if that search really finds the missed listings.
Read far enough down
A search returns a page of results. We ask for up to 200 at a time. Each dot here is one result.
Busy cards have more listings than one page holds, so we keep reading, page after page, up to 1,000 results. A listing sitting at number 350 still counts.
Is this title this card?
Every title gets four checks. First the grade: PSA, BGS, CGC, SGC, TAG or ACE, and the number. CGC, TAG and SGC Pristine and CGC Perfect 10 are their own grades, and so is BGS Black Label. A Pristine 10 is never mixed in with plain 10s.
Then the card number, and its set total when the title has one. 215/203 is a different card from 215/198.
Then the printing. Words like Alt Art, Manga or SP mean a different version of the card, with its own price.
Last, the language lane: English and Japanese copies are kept apart. When all four agree, the listing attaches to the card.
Safety rails
Some signs in a title mean it's another card, even when the name matches:
Collectors can fix it too
If you see a listing on the wrong card, flag it. It disappears for you right away.
If you know a listing we're missing, paste its link. ATLS works out why it was missed, then checks it against the same rules as every other listing.
If the rules agree, it's added. If they don't, an admin reviews it.
Admins can confirm a listing, remove it, move it to the right card, or change its language. Every change can be undone.
How we know it works
Every listing we judge goes into a log, along with the decision and the reason. When something goes wrong, we can see exactly which rule made the call.
Replay before release
Before any rule change ships, we replay it against past decisions people made by hand. If the new rule disagrees with them, we find out before it reaches a card.
Is our cheapest really the cheapest?
Every night, we check the cheapest listing we show against a fresh look at the marketplace. If there's a cheaper copy we didn't show, we want to know why.
A deep read every week
Once a week we take 20 cards and read much deeper than the regular job does, to find every listing that exists for them. Comparing that with what we showed gives our true recall: out of all the listings out there, how many we found.
eBay in its own group
eBay listings are shown in their own group on a card, apart from other marketplaces, as eBay's license requires.
Search wide, read deep, judge carefully, and keep checking.
Spot a listing on the wrong card, or one that's missing? Flag it or paste it from the card's page. It helps everyone who looks at that card after you.