x-assembled-from
`x-assembled-from` appears in the info block. Its value is a list. Used by 4 providers across 5 OpenAPI documents. Observed values include `506 per-endpoint OpenAPI fragments published at https://developer.synup.com/
Where it appears
| Location in the document | Occurrences | |
|---|---|---|
| root | 1 | |
| info | 4 |
What its value looks like
| Value shape | Occurrences |
|---|---|
| array | 2 |
| object | 2 |
| string | 1 |
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.