Data & schema semantics · Validation & constraints

x-fieldValidation

`x-fieldValidation` appears on schema objects and properties. Its value is a string. Used by a single provider across 1 OpenAPI document. Observed values include `required`, `size(_,255)`, `required size(1,50)`, `size(1,15)`. Consistent with validation & constraints — 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.

28 occurrences

1 documents

1 providers

purpose-named

Where it appears

Location in the document	Occurrences
schema	28

What its value looks like

Value shape	Occurrences
string	27
object	1

Observed values

Sampled from the specifications, most frequent first.

requiredsize(_,255)required size(1,50)size(1,15)size(1,4)size(3,3) regex([A-Z]*)required has_textsize(_,50) regex(^[a-zA-Z0-9_-]+$)

Providers publishing it

All 1.

weavr

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.