What's New in APIs.json 0.23

APIs.json 0.23 is a vocabulary release, the same shape as 0.22 and a great deal smaller. It registers eight property types and repairs the reserved words listing. No structural change, no new collections, no new required fields.

0.22 was a coverage release. This one is a precision release.

0.22 moved real-world property validity from 67.6% to 93.5% by promoting sixty-four types that thousands of organizations were already publishing. Measured again today, against 26,866 indexes on the same basis, 94.4% of top-level common property references validate under 0.22, and 94.5% under 0.23.

That is a gain of 161 references. It is not much and it is not supposed to be. The high-volume backlog is cleared; what is left is a long tail, and the interesting question about a long tail is not how many references it holds but who trips over it.

What prompted it

A scoring pipeline. The APIs.io rating rubric reads an index and asks whether a provider has declared machine-readable authentication, or a consent signal, or the standard they conform to. It was asking for vocabulary the specification rejected. A provider could publish exactly the property the rubric wanted and fail schema validation for doing it.

That is the wrong way round. If a consumer is looking for a property type, the specification should have a word for it.

Eight types promoted

Counted across 26,866 published indexes, reading only the type field of entries in properties, common, prompts, rules and workflows. 162 organizations publish at least one of them.

• ContentSignal — 67 organizations. The Content-Signals directive in robots.txt: how a provider permits its content to be used for search, AI input, and AI training. Distinct from AgenticAccess, which says whether agents may call an API, and LLMsTxt, which says what an agent should read. ContentSignal is where the terms are stated.
• APIKeys and APIKey — 28 organizations across the family. Key issuance, rotation and revocation as its own property rather than folded into Authentication. Which scheme is in use and how you obtain the credential are different questions, and the second is the one that blocks integrations.
• Certification — 27 organizations. The conformance testing programme an integrator must pass. The process, where Conformance is the result.
• Standard — 16 organizations. The singular of Standards, which 0.21 already registered. A provider pointing at one standard should not have to pluralise it.
• Licensing — 25 organizations. Licensing terms for the data or content an API serves, distinct from License (the software licence on SDKs) and InterfaceLicense (the licence on the interface).

0.23 also accepts API Key and API Keys as synonyms of APIKeys, continuing the position 0.22 took: the canonical name is documented and publishers should prefer it, but a specification that accepts one spelling of a word the world spells four ways does not produce consistency, it produces extensions.

The reserved words listing was 117 types behind

This is the part worth reading if you have ever validated against the listing rather than the schema.

The reserved words section of the specification text — the human-readable listing of every property type — was never updated for 0.22. Every one of the sixty-four types promoted in that release, plus seven promoted in 0.21, were accepted by the JSON Schema and absent from the listing that documents it. DomainSecurity, on 23,135 indexes, was not in it. Nor were LLMsTxt, AgenticAccess, SBOM, OAuthScopes, or MCPServer.

Two artifacts, one vocabulary, silently disagreeing. Anyone reading the specification to find out what they were allowed to publish got an answer 117 types short of the truth.

In 0.23 the listing is generated from the schema and the two are verified to agree: 197 canonical types and 48 accepted synonyms, all present in both.

The canonical files

The specification text and JSON Schema live in the api-json repository as apisjson_0.23.txt and schema_0.23.yml. If a type you publish is still invalid and you think it should not be, open an issue — every type in this release got there because someone published it first.