API Evangelist — OpenAPI Extensions

The x- namespace is where API providers put everything OpenAPI would not hold. This section is the reference for it: every extension found in the as-published OpenAPI specifications across the APIs.io network, what each one appears to do, where in a document it sits, what its value looks like, and who publishes it.

Generated. Do not hand-edit. Everything under _extensions/, _purposes/, _data/ and search-index.json is written by api-search/network/scripts/build_extensions.py, which runs as part of the network build. Edit the builder, not the output.

Descriptions are derived, not authored

Most extensions have no published definition anywhere. Rather than invent one, each description is assembled from measured evidence — the locations a key appears in, the shape and sample values it carries, and how many providers use it — and hedged accordingly. Curated descriptions can be supplied in network/_data/extensions_curated.yml; those are marked as curated on the page so the two are never confused.

The same collection is published to extensions.apievangelist.com.

What was here before

This repository previously held four documents describing API Evangelist platform extensions — AT Protocol, JSON Schema, Open Policy Agent, OpenAPI — a different sense of the word “extension” than the one this site now serves. They are preserved under _legacy/_store/ rather than deleted, and are not built. Its _config.yml also carried a stale url: contracts.apievangelist.com, now corrected to this site’s own domain.