Documentation & DX

x-group-key

`x-group-key` appears on schema objects and properties. Its value is a string. Used by a single provider across 1 OpenAPI document. Observed values include `Level III - Order`, `Level III - Line Item(s)`, `Payment Facilitator`, `Recurring`. Consistent with documentation & dx — this is inferred from where the key appears and what it carries, not from any published definition.

Documentation & DX derived description
How this description was produced. It is assembled from what was measured in the corpus — where this key appears in a document, what shape its value takes, the values observed, and how many providers use it. It is not taken from a published definition, because for most extensions none exists. Read it as evidence, not as a specification. If you own this extension and want it described properly, tell us.
55 occurrences
1 documents
1 providers
purpose-named

Where it appears

Location in the documentOccurrences
schema 55

What its value looks like

Value shapeOccurrences
string55

Observed values

Sampled from the specifications, most frequent first.

Level III - OrderLevel III - Line Item(s)Payment FacilitatorRecurringCustomer VaultCustomer Token Vault

Providers publishing it

All 1.

nmi

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 documentation & dx job.