Documentation & DX

x-tag

`x-tag` appears on schema objects and properties. Its value is a string. Used by 18 providers across 19 OpenAPI documents. Observed values include `articles`, `institutions`, `common`, `projects`. 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.
1576 occurrences
19 documents
18 providers
purpose-named

Where it appears

Location in the documentOccurrences
schema 1502
operation 74

What its value looks like

Value shapeOccurrences
string1576

Observed values

Sampled from the specifications, most frequent first.

articlesinstitutionscommonprojectscollectionsauthorsfundingother

Providers publishing it

All 18.

deakindtuerasmus-university-rotterdamfigsharefrontegghbkula-trobe-universityloughboroughmacquariestockholmuniversity-of-adelaideuniversity-of-aucklanduniversity-of-canterburyuniversity-of-rochesteruniversity-of-sheffielduniversity-of-sussexuniversity-of-the-witwatersranduon

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.