x-content-type
`x-content-type` appears on operations. Its value is a string. Used by 6 providers across 9 OpenAPI documents. Observed values include `application/json`, `application/octet-stream`, `application/x-www-form-urlencoded`, `multipart/form-data`. Consistent with type system — 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 | |
|---|---|---|
| schema | 11 | |
| operation | 125 |
What its value looks like
| Value shape | Occurrences |
|---|---|
| string | 136 |
Observed values
Sampled from the specifications, most frequent first.
Providers publishing it
All 6.
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.