Data & schema semantics · Type system

x-nullable

`x-nullable` appears on schema objects and properties. Its value is a boolean flag. Used by 48 providers across 185 OpenAPI documents. Consistent with type system — this is inferred from where the key appears and what it carries, not from any published definition.

Data & schema semantics 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.

40972 occurrences

185 documents

48 providers

purpose-named

Where it appears

Location in the document	Occurrences
schema	40460
operation	145
tag	30
parameter	261
server	13
components	8
header	3
response	52

What its value looks like

Value shape	Occurrences
boolean	40968
string	4

Observed values

Sampled from the specifications, most frequent first.

truefalse

Providers publishing it

All 48.

1fort alayacare altr anchorage aptible bigcommerce business-software-and-services-reviews-g2 clear-street clevergy cloudera cohesity docker doordash elastic-path emarsys eon esper fleetmon flume-health form3 g2 galatea-bio goharbor griffin haproxy hatchet hootsuite ironscales isovalent leaflink lianlian-global limitless-ai listrak lufthansa-cargo magic-moment measurabl microsoft-azure oracle passbolt podman punchh secureauth spectro-cloud takealot tiledb toast wazo wealth-reader

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.