x-pattern
`x-pattern` appears on operations and on schema objects and properties. Its value is a string. Used by 4 providers across 4 OpenAPI documents. Observed values include `[\\u0020-\\uD7FF\\uE000-\\uFFFD\\uD800\\uDC00-\\uDBFF\\uDFFF\\r\\n\\t]*`, `[\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\t]*`, `[\u0020-\uD7FF\uE000-\uFFFD\uD800\uDC00-\uDBFF\uDFFF\r\n\t]*`, `[\\u0020-\\uD7FF\\uE000-\\uFFFD\\uD800\\uDC00-\\uDBFF\\uDFFF\\r\\n\\t]\\+`. Consistent with validation & constraints — this is inferred from where the key appears and what it carries, not from any published definition.
Where it appears
| Location in the document | Occurrences | |
|---|---|---|
| operation | 108 | |
| schema | 49 |
What its value looks like
| Value shape | Occurrences |
|---|---|
| string | 157 |
Observed values
Sampled from the specifications, most frequent first.
Providers publishing it
All 4.
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.