x-parent
`x-parent` appears in the document and on schema objects and properties. Its value is a string. Used by 7 providers across 8 OpenAPI documents. Observed values include `Brand Kits`, `true`, `Layers`, `apilayer`. Consistent with identity & relationships — this is inferred from where the key appears and what it carries, not from any published definition.
Where it appears
| Location in the document | Occurrences | |
|---|---|---|
| other | 14 | |
| info | 2 | |
| schema | 6 |
What its value looks like
| Value shape | Occurrences |
|---|---|
| string | 17 |
| boolean | 5 |
Observed values
Sampled from the specifications, most frequent first.
Providers publishing it
All 7.
Why this is not in OpenAPI
Extensions exist because a provider needed something the specification would not carry. Most of what they hold is not the API contract at all — it is operational metadata about the contract: documentation, lifecycle, policy, provenance, and now agents. That metadata is usually better placed alongside the contract, in an Overlay or an APIs.json index, than crammed inside it. See everything else doing the data & schema semantics job.