AI product feeds for one-of-one inventory

01

Three identifiers, carried together

Applies to marketplace onlyown storefronthybrid

The record carries three identifiers, and a validator expects all three populated before it examines anything else.

The middle row is the one selling platforms rarely supply, and the rest of the record attaches to it. Choosing its value, deciding what an absent manufacturer code should record, and resolving duplicates are covered in the identity lesson; this lesson assumes the three values are in hand.

The fourth column separates the failures because they arrive differently. The first two are data errors. The second is the one that surfaces weeks later as a dispute about which object a buyer received, since nothing in the record distinguishes them.

02

Merge and relist are different writes

Applies to marketplace onlyown storefronthybrid

Two operations look alike in a spreadsheet and are not the same write. A relist keeps the physical-item identity and issues a new offer or offer version. A merge retires one physical-item identity in favor of another and redirects it, which corrects identity rather than recording a commercial event.

A system that treats both as “make a new listing” can reprice one object twice or return a sold object to availability, and a validator cannot distinguish the two cases unless the record does. Channel listing IDs are references onto the object and the offer, so they are stored beside the physical-item identity rather than in place of it.

03

The minimum record

Applies to marketplace onlyown storefronthybrid

The downloadable v0.1 specification requires a stable item ID, a stable offer ID, title, canonical URL, exact-item images, normalized and narrative condition, currency and minor-unit price, availability state, quantity, observation time, version, seller link, and policy links. The accompanying JSON Schema checks shape, and the validator adds cross-field lifecycle rules.

These fields come from the cited specifications rather than from this course. OpenAI’s current product API requires stable product and variant identifiers and exposes price, availability, condition, media, and seller links.¹ The Schema.org Product vocabulary represents the same commercial facts on a page,² alongside the Offer vocabulary for price and availability.³ Neither vocabulary synchronizes inventory between systems. The v0.1 record is written once so that one answer serves every destination.

A record can be well-formed and still state that an item is available in a quantity of zero, or that a sale occurred before the state was last observed. Those are agreements between fields, which is the second row.

Prices are stored in minor units. Decimal representations accumulate rounding differences as they are parsed and re-serialized across systems, and minor units remove that difference.

04

Facts that can be checked

Applies to marketplace onlyown storefronthybrid

A checkable claim is one a buyer or reviewer can trace to something specific. Three groups of fields carry them.

• Factual title, condition label, notes, defects, inspection date, and photographs of the exact unit.
• Price and currency paired with availability state, timestamp, shipping, return, and geographic limits.
• Authenticity stated only where a verification step exists to point at.

Where a fact lives determines whether anything can check it. A defect described only in a paragraph is not reachable by a validator or by a system reading the record mechanically. The same defect in a condition field with an inspection date beside it can be compared against the grade and flagged when the two disagree. What to put in those fields, and how far a claim can go, is the subject of the evidence lesson.

05

Three required condition fields

Applies to marketplace onlyown storefronthybrid

Condition is three required fields rather than one: a normalized value, unit-specific narrative and media, and an inspection date. A record supplying only the first passes a shape check and carries nothing specific to the object.

The validator enforces the pairing, not the content. It can require that a grade never stands alone, that media is present, and that the assessment carries a date comparable against the other timestamps. It cannot determine whether the grade is accurate or whether the photograph shows the object in hand, which is why writing those values is covered separately.

06

Designing for quantity races

Applies to marketplace onlyown storefronthybrid

A quantity of one does not prevent two channels from acting on stale state. The record uses a version token or an equivalent conditional update, defines when a reservation becomes authoritative, and makes sold or withdrawn terminal for the current offer.

A version token works by a single rule: a writer reads the record along with its current version, and the update is accepted only if the version is still what it read. If something else changed the record first, the update is rejected and the writer re-reads. The rule converts a silent race into a returned error.

Where cross-channel reservation is unavailable, the record states that as an operational limit and the verification interval is shortened, leaving the residual risk manual. The description that causes trouble later is “synchronized,” because it will be relied on by whoever next decides how many channels to add.

07

The lifecycle transitions

Applies to marketplace onlyown storefronthybrid

Each transition below is a point where the record and the world can diverge. Naming them is what makes the divergence detectable.

1. Create a full record with a version.
2. Reserve only where the merchant process can actually prevent a conflict.
3. On sale, make the source unavailable and propagate removal.
4. Verify every surface, then retain a truthful tombstone or redirect.

The fourth step contains two verbs on purpose. Propagation and verification are separate actions with separate failure modes, and the record carries the surface list that verification walks. How long that walk takes on a given setup is measured in the removal-latency lesson.

The second step is conditional for a reason. A reservation that cannot prevent a competing sale records a protection the system does not provide, and the record then states something that is not the case.

08

Accepted and rejected test records

Applies to marketplace onlyown storefronthybrid

The fixtures are the executable form of the rules above. Each rejected case is a record a shape-only check accepts, and each reason names the cross-field rule that catches it.

Rejecting on ambiguity is the default here because the two error directions cost differently. A rejected record costs a listing. An accepted contradictory record for a single object can sell it twice.

The rejected fixtures are run alongside the accepted ones. A suite that only demonstrates good records passing continues to pass after a rule is loosened; the negative fixtures are the ones that fail at that point.

09

Adopting the record without new software

Applies to marketplace onlyown storefronthybrid

The specification describes a record shape. A seller running a spreadsheet and two marketplace accounts can satisfy most of it with three columns: a physical-item column that never changes, an inspection-date column beside the condition grade, and an observed-at timestamp beside availability. Those three turn a row from an assertion into a dated observation.

A column only helps if something moves the timestamp when the value moves, which is the practice covered under removal latency.

One adjacent finding is often read as more than it says. Peer-reviewed catalog-quality work reports reference-backed record repair using brand knowledge bases and agents, conducted inside the authors’ own large-retailer setting.⁴ It reports results for structured catalog facts in that setting. It does not describe a service that assesses a seller’s own stock, and the evidence lesson covers why.

Applied to the camera, the row carries four columns, one of which has no value yet.

The adoption order follows the cost of each failure. Identity first, since everything attaches to it and retrofitting it onto historic rows is the largest job. Lifecycle second, where a sale can go wrong. Condition evidence third, where returns and disputes arise. A partial adoption that records which parts are done is a usable state to be in.

10

What the record requires

Applies to marketplace onlyown storefronthybrid

The v0.1 record requires three identities, a condition grade paired with unit-specific evidence and an inspection date, price in minor units with currency, availability with an observation time, a version token, and defined lifecycle transitions ending in a verified removal.

The field requirements are drawn from a product API that requires stable product and variant identifiers,¹ and from vocabularies that represent the same commercial facts on a page.² Price and availability come from the Offer vocabulary.³ None of the cited documents specifies how a seller resolves a race between two channels, and none of them synchronizes inventory; those remain the seller’s process.