The AON category taxonomy is the controlled set of Protocol v1 category IDs used in Offer and Query contracts.
Partners place an Offer under a valid primary category, while Agents and Developers can send valid category IDs under constraints.category_ids when a deterministic category filter is appropriate. Parent IDs match their descendant subtree; unknown or invented IDs are invalid and must not be silently reinterpreted.
Category taxonomy in AON
AON uses Taxonomy v1 to keep Partner Offer classification and public Query constraints interoperable. The published vocabulary helps Partners classify supply consistently and gives Developers deterministic filters they can validate. The docs and active category tools expose the registry and matching rules; the AgentOffer sources remain authoritative for exact fields.
Browse the AON category taxonomyHow category IDs work
Resolve a valid ID
Use the published AON Taxonomy v1 registry or the active category tools; never invent a category string from a display name.
Classify the Offer
A Partner assigns the best-fit valid primary category to offer_info.category.id and may provide secondary categories when supported.
Apply an explicit filter
A Developer adds constraints.category_ids only when the user or product has a clear deterministic category requirement.
Match the hierarchy
A parent category matches its descendants, so broad IDs can serve broad intent while deeper IDs narrow the eligible set.
Category taxonomy roles
The same registry supports supply classification and consumer-side Query filtering, but the fields have different responsibilities.
| Concept | Meaning |
|---|---|
| Primary Offer category | offer_info.category.id is the canonical display classification for a returned or supplied Offer. |
| Secondary categories | offer_info.secondary_category_ids can describe additional taxonomy meanings when the current schema supports them. |
| Query constraints | constraints.category_ids are deterministic filters that make a category requirement explainable and testable, not a replacement for the natural-language intent field. |
| Fallback | Use others only when no published category describes the Offer or intent; prefer a valid top-level category whenever one applies. |
- A category ID is not a user-facing category name and must not be invented from an internal taxonomy.
- Category filtering is optional context; it is not an automatic second request after every Offer Query.
- A category match does not prove current price, availability, or checkout eligibility.
Category taxonomy vs intent matching
The taxonomy provides canonical deterministic IDs for classification and filtering. Intent matching interprets the user's expressed request and helps evaluate relevance. A category ID should complement a known constraint, not replace the user's intent. See the Intent matching definition.
Example in practice
A user asks for hiking socks. The Agent uses a valid hiking category ID only when a category constraint is explicit, while the natural-language request remains in intent. A Partner classifies a matching Offer under its most specific valid category.
Common questions about category taxonomy
Where do category IDs belong in a Query?
Use canonical IDs under constraints.category_ids when an explicit deterministic category filter is appropriate. Keep the user's natural-language request in intent.content.
Can a parent category match child categories?
Yes. A parent ID matches its full descendant subtree under the current taxonomy semantics.
What happens when a category ID is unknown?
Unknown or invented IDs are invalid. Resolve the category through the published registry or active category tools instead of silently treating it as a display name.
What category should a Partner assign to an Offer?
Use the most specific valid category that the Partner can support confidently. A valid Level 1 category is preferable to an unrecognized or over-specific ID.
Sources
- AON Category TaxonomyAON documentation
- AgentOffer Protocol v1.0 sourcesAON specification
- AgentOffer v1.0 schemasAON specification
- Read the Offer Query referenceAON documentation