Regulatory Posture applies to this provider. Its tags matched the Horizontal (data, software, accessibility, platform) regime, so Regulatory Posture carries 15 points of the composite. If this regime is wrong for your business, say so on your provider repo — the applicability map is public and we will correct it.

Create-or-Update Ergonomics could not be measured. We hold no machine-readable contract for this provider to read, so there is nothing to measure a write surface against. Excluded rather than scored zero: never-measured and measured-empty are different facts. Publishing an OpenAPI is what makes this facet — and several others — scorable at all.

The six quality facets above are damped to 85 points between them, because the conditional facet above carries the other 15. That is why each facet's contribution is shown against a damped maximum: raising a quality facet moves the composite by 85% of its nominal weight, not 100%. The full arithmetic is at apis.io/rating/.

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<a href="https://apis.io/providers/crossref-metadata-search/"><img src="https://apis.io/badge/crossref-metadata-search/card.svg" alt="Crossref Metadata Search on APIs.io — Kin Score by API Evangelist"></a>

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Agent readiness — checks not met, largest first (exact, from this profile):

Machine-Readable Contract +18 pts — api_specs includes an OpenAPI document Ask about this →
MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship Ask about this →
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author Ask about this →
Machine-Readable Auth +10 pts — a served openid-configuration/oauth-authorization-server carrying `issuer` (served), else the securitySchemes class in the provider OpenAPIs — bound (mutualTLS, DPoP, Signature) > negotiable (oauth2 authorizationCode/clientCredentials, openIdConnect) > bearer (http bearer, apiKey) Ask about this →
Idempotency +9 pts — OpenAPI mutating operations declare an idempotency key — a header, a request-body property, or a named de-duplication token whose own description says so (verified); else common[].type matches /idempoten/i (documented) Ask about this →
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes Ask about this →

13 more unmet checks in the Agent Readiness table above.

Kin Score — facets with the most composite points still available (weight × headroom):

Contract Quality scores 0.0 — up to +25.0 composite points Ask about this →
Access Clarity scores 0.0 — up to +20.0 composite points Ask about this →
Developer Ergonomics scores 9.5 — up to +18.1 composite points Ask about this →

Each check links to what satisfies it. Publish the artifact, or tell us where it already lives, and the score moves on the next scoring run.

Not sure how this applies to your stack? Ask about any one item. Kin Lane reads every question, looks at your profile and your situation, and replies with what a fix would take — scoped to that one area, priced up front, yours whether you ship it or not. Ask a question →

Improve this rating by publishing the missing artifacts — every area above can be raised, and the full rubric is at apis.io/rating/. Every facet and dimension name above is a link: it opens that measurement's own page — what it means, the exact checks that feed it, how the whole catalog distributes on it, and the providers at the top of it. This rating is computed from the provider profile at artifacts.apis.io/crossref-metadata-search/apis.yml: open an issue on github.com/api-evangelist/crossref-metadata-search to ask a question or point us at an artifact you publish. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 1

Individual APIs this provider publishes, each with its own machine-readable definition.

Crossref Metadata Search

Books & Articles Metadata

Resources

Company 1

The organization behind the API

Website

Website

Other 1

Properties that don't map to a standard resource type

PublicAPIsListing

PublicAPIsListing

Source (apis.yml)

aid: crossref-metadata-search
deliveryModel:
  model: unknown
  open_source: false
  commercial: false
  callable_host: false
  label: Delivery model not determined — needs a product licence on record
  confidence: low
  source:
  - none
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source: []
  generated: '2026-11-13'
  method: derived
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/icons/crossref-metadata-search.png
name: Crossref Metadata Search
description: Books & Articles Metadata
url: https://github.com/CrossRef/rest-api-doc
specificationVersion: '0.23'
created: '2026-05-28'
modified: '2026-05-28'
x-source: public-apis/public-apis
x-category: Books
x-tier: 3
x-tier-reason: bulk-registered-from-public-apis
tags:
- Books
- Public APIs
apis:
- name: Crossref Metadata Search
  description: Books & Articles Metadata
  humanURL: https://github.com/CrossRef/rest-api-doc
  tags:
  - Books
  properties:
  - type: Documentation
    url: https://github.com/CrossRef/rest-api-doc
common:
- type: Website
  url: https://github.com/CrossRef/rest-api-doc
- type: PublicAPIsListing
  url: https://github.com/public-apis/public-apis
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com

Crossref Metadata Search API — frequently asked questions

Does Crossref Metadata Search have an API?

Yes. APIs.io lists 1 API from Crossref Metadata Search, including Crossref Metadata Search.

Is the Crossref Metadata Search API ready for AI agents?

Crossref Metadata Search has a Kin Score of 3.6 out of 100 (minimal) and an Agent Readiness score of 0.0 (human-only), scored by API Evangelist on 2026-11-13.

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Tools for providers

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find_providersBrowse and filter every provider in the catalog.
get_provider_artifactsEvery artifact this provider publishes, grouped by type.
get_provider_operationsEvery operation across all of their OpenAPIs — one call instead of parsing every spec.
get_provider_toolsEvery MCP tool they ship, with the operation each wraps.
get_provider_evidenceHow each part of their score was established. Free — the basis for a claim should not sit behind it.
get_provider_ratingPRO — composite, band, trend and facet scores.
apis_io_searchSTART HERE — APIs, providers and tags for one query, each with its total.
resolveTurn a domain, URL or GitHub org into the provider it belongs to.
find_cohortsEvery scored population of providers in the catalog.

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