Data & schema semantics · Type system

x-nullable

`x-nullable` appears on schema objects and properties. Its value is a boolean flag. Used by 31 providers across 121 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.

4379 occurrences

121 documents

31 providers

purpose-named

Where it appears

Location in the document	Occurrences
schema	4037
tag	15
operation	20
parameter	255
response	52

What its value looks like

Value shape	Occurrences
boolean	4377
string	2

Observed values

Sampled from the specifications, most frequent first.

truefalse

Providers publishing it

All 31.

1fort alayacare altr anchorage aptible bigcommerce business-software-and-services-reviews-g2 clear-street clevergy docker elastic-path eon esper fleetmon griffin hatchet hootsuite ironscales isovalent lianlian-global limitless-ai listrak microsoft-azure oracle passbolt podman punchh takealot toast toast-tab wazo

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.