x-summary
`x-summary` appears on response objects. Its value is a string. Used by 19 providers across 77 OpenAPI documents. Observed values include `Success`, `Unauthorized`, `Internal server error`, `Not found`. Consistent with documentation & dx — 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 | |
|---|---|---|
| response | 1993 | |
| header | 1 | |
| path | 111 | |
| securityScheme | 9 | |
| info | 20 | |
| operation | 5 | |
| root | 3 |
What its value looks like
| Value shape | Occurrences |
|---|---|
| string | 2127 |
| object | 10 |
| empty | 5 |
Observed values
Sampled from the specifications, most frequent first.
Providers publishing it
All 19.
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 documentation & dx job.