Used goods and surface eligibility

01

What the specifications assume about a product

Applies to marketplace onlyown storefronthybrid

Product APIs in this space are built around stable identifiers and repeated variants. OpenAI’s product specification requires stable product and variant IDs and exposes price, availability, condition, media, and seller links.¹ Each of those fields is answerable for a used item. The strain is in what a variant model implies rather than in the field list.

A variant model treats a product as an abstraction and the shipped object as an instance of it. For manufactured goods that holds. For a 1978 camera with one specific scratch, the abstraction and the instance are the same object, and no upstream catalog contains an entry describing it.

Two statements follow, and they are separate. The specification does not exclude used goods — no clause says so, and the fields are fillable. It answers a question resale does not have, which of the identical units is being purchased, and leaves the resale question, what specifically is wrong with this unit, to fields sized for a shorter answer.

02

Identity without a shared catalog

Applies to marketplace onlyown storefronthybrid

The requirement to supply stable IDs is met directly.¹ Assign an identifier when the item enters inventory, do not reuse it, and do not change it when the item is re-photographed or re-listed. Applied from intake this costs nothing; applied retroactively across existing stock it is a data project.

External identifiers are the harder field. Merchant documentation states product-attribute requirements for its checkout path, and those attribute lists are where the catalog assumption becomes concrete.² Some fields have no true value for a given item. The entry for those is what is true, a blank where nothing is true, and a note recording which of the two applies.

Three of those rows are answered once the intake discipline exists. The third is answered by leaving the field empty and recording a one-line reason, which is a different entry from an omission and reads differently to anyone who checks it later.

03

The condition field and what sits beside it

Applies to marketplace onlyown storefronthybrid

Condition is an exposed field in the product specification, so resale stock is not outside the model here.¹ The field carries a bucket value. For a new manufactured good that value is close to the whole of what a buyer needs about condition. For a used camera it is one input among several.

The specifics — where the scratch is, whether the meter works, what was replaced and when — go in the description and the photographs, which any system reading the item reads as well. A correctly filled condition field paired with a vague description satisfies the requirement and leaves the buyer’s question open.

For this camera the bucket value is “used”, which is accurate. Alongside it, the description records that the shutter is dependable at faster speeds and unreliable below them, and that there is a scratch on the base plate that does not affect operation. Those are the facts a buyer acts on, and no structured field on the page has a place for them.

04

One unit makes one availability transition

Applies to marketplace onlyown storefronthybrid

Availability is an exposed field like the others. For catalog goods it moves in both directions. For one-of-one stock it moves once, from one to zero, and does not return. Everything downstream holding a cached copy of the item is inaccurate from that moment until it refreshes.

Etsy’s documentation covers a subset of its listings, purchasable through the AI shopping surfaces it names, for shoppers it identifies as eligible in the United States.³ Where such a path applies, the sale may originate outside the interface a seller is watching, so the removal path needs to be at least as fast as the fastest purchase path.

The same sentence limits its own scope in the other direction. It covers a subset of listings, so a documented path at a marketplace does not establish that a specific item participates.³ The two readings lead different places: one produces a recorded exposure wider than the documents support, the other leaves a removal interval unmeasured.

05

Where eligibility is a permission question instead

Applies to marketplace onlyown storefronthybrid

At some venues the question is not about fields. eBay’s current agreement forbids three kinds of automation absent express advance permission: agents that shop for a person, bots running on a language model, and order placement with no human in the loop.⁴ That text addresses automation, not the category of goods being sold, so whether stock is second-hand does not bear on it in either direction.

The two questions have different kinds of answer. Whether a system can represent an item is a data question answered field by field. Whether a system may transact at a venue is a permission question answered by that venue’s policy. A complete record is an answer to the first only.

06

A field-by-field pass, item in hand

Applies to marketplace onlyown storefronthybrid

The method is one pass with the item present, taking each required attribute in turn. The first item takes the longest, because the decisions it produces apply to the rest of the stock.

1. Assign a stable internal ID and record where it is stored, since an ID that cannot be found later serves no purpose.
2. Mark each required attribute as true-and-supplied, true-but-unknown, or not-applicable — three states, since two states force a choice between them.
3. Leave not-applicable fields blank rather than converting them to a plausible value, and leave unknown fields blank rather than converting them to a default; both substitutions pass validation.
4. Put the bucket value in the condition field and the specifics in the description and photographs.
5. Check that the same figures appear on every surface carrying the item.
6. Keep the blanks as a list, which is also the answer when a surface asks why a field is empty.

Run to completion on the camera, the pass produces four lines, two of them blank.

The list of blanks records which requirements this item does not meet and why, separated into the ones that could still be established and the ones that never will be. It is also the input to any later decision about whether a given surface is worth the work.

07

What the requirements ask of unique stock

Applies to marketplace onlyown storefronthybrid

The product specification requires stable product and variant IDs and exposes price, availability, condition, media, and seller links.¹ Merchant documentation states product-attribute requirements for its checkout path.² Neither document contains a clause excluding used goods, and neither describes how to represent an item with no shared external identifier.

Alongside the field requirements sit two venue-level facts: Etsy documents purchasing through named AI surfaces for a subset of listings and eligible US shoppers,³ and eBay’s agreement conditions automated purchasing on express advance permission.⁴ Those are answered by reading policy rather than by completing fields.