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Crossref

Crossref is a non-profit organization that provides digital infrastructure for scholarly communications. Best known for Digital Object Identifier (DOI) registration, Crossref also operates a public REST API offering searchable, filterable access to metadata for tens of millions of scholarly works, journals, members, funders, prefixes, types, licenses, and DOI registration agency information. The Crossref REST API supports free-form queries, field queries, filters, facets, deep-paging cursors, and selection of specific elements, and is used by reference managers, repositories, discovery layers, and analytics platforms.

agent aware

Real signal across most facets with visible, nameable gaps — the contract exists but is thin, or the portal is good while governance and commercial terms are absent.

Kin Score

API Evangelist profiles Crossref the way a machine reads it — 19 machine-readable artifacts across 8 APIs, pulled from the provider's own public surface and indexed so a developer, an analyst, or an AI agent can evaluate it against every other provider on the network.

Every provider in the network is reduced to the same set of machine-readable artifacts — OpenAPI contracts, event specifications, GraphQL schemas, runnable collections, pricing and rate-limit signals, security posture, OAuth scopes, and the agent surfaces (MCP servers and skills) that let software drive the API on its own. We profile them because the interface is the part of a company you can actually inspect: it is a truer signal of what a provider does than any marketing page. From those artifacts we compute the Kin Score — Crossref scores 56.2/100 (developing), with a separate agent-readiness read of 39/100 (agent aware). The full breakdown is below, followed by every artifact we hold — each card links through to its machine-readable definition on apis.io.

Kin Score

This is the API Evangelist rating — a single, repeatable read computed from the artifacts on this page. Green fill is points earned; the red track is points possible, so every bar shows earned-versus-possible at a glance.

Kin Score Kin Score How this is scored →
scored 2026-07-27 · rubric v0.5
Composite quality — 56.2/100 · developing
Contract Quality 14.6 / 25
Developer Ergonomics 4.3 / 20
Commercial Clarity 10.0 / 20
Operational Transparency 6.8 / 13
Governance 10.4 / 12
Discoverability 10.0 / 10
Agent readiness — 39/100 · agent aware
Machine-Readable Contract 18 / 18
Agentic Access Contract 15 / 15
MCP Server 0 / 12
Machine-Readable Auth 0 / 10
Idempotency 0 / 9
Stable Error Semantics 0 / 8
Request/Response Examples 0 / 7
Rate-Limit Signaling 7 / 7
Typed Event Surface 0 / 6
Agent Skills 0 / 5
Well-Known Catalog 0 / 4
Consent & Bot Identity 0 / 3

How we profile Crossref

Each block below is one kind of artifact we hold for Crossref. For each we say what it is and why it earns a place in the profile, then list every one we've indexed — capped at two rows, scroll within the panel for the rest.

APIs 8

Each API is captured as its own OpenAPI definition — every operation, parameter, and response. This is the single most useful machine-readable description of what an API does, and it's what lets us score, lint, mock, and generate against it without asking the provider for anything.

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

Crossref Agency API

The Agency API from Crossref — 1 operation(s) for agency.

Crossref Funders API

Endpoints that expose funder related data

Crossref Journals API

Endpoints that expose journal related data

Crossref Licenses API

Endpoints that expose license related data

Crossref Members API

Endpoints that expose member related data

Crossref Prefixes API

Endpoints that expose prefix related data

Crossref Types API

Endpoints that expose type related data

Crossref Works API

Endpoints that expose works related data

Scroll within the panel for all 8 ·

Open Collections 1

Open, tool-agnostic collections carry the same runnable value as Postman without locking you to one client — the portable, forkable form of the same exercise.

Open, tool-agnostic API collections (OpenAPI-derived and Bruno).

Crossref

OPEN COLLECTION

Pricing Plans 1

Pricing is part of the interface. Machine-readable plans tell you what a tier costs and includes before you commit — one of the six things the Kin Score reads for commercial clarity.

Published pricing tiers and plan structures.

Rate Limits 1

Rate limits are the difference between a demo that works and a production integration that doesn't fall over. Publishing them is an operational-transparency signal — and a hard requirement for any agent that plans its own throughput.

Documented rate limits and quota policies.

Crossref Rate Limits

5 limits

RATE LIMITS

FinOps 1

Cost, billing, and metering signals let a buyer model the financial operations of an API before it's live. We profile them for the same reason we profile pricing: the money is part of the contract.

Cost, billing, and metering signals for API financial operations.

Semantic Vocabularies 1

JSON-LD contexts give the data shared meaning across APIs. We profile them because semantics are what let a machine reconcile 'customer' here with 'customer' somewhere else.

JSON-LD contexts and semantic vocabularies used across these APIs.

Crossref Context

36 classes · 12 properties

JSON-LD

Spectral Rules 2

Governance rulesets we run against this provider's specs — the automated checks behind parts of the score. Profiling them makes the quality bar explicit and re-runnable, not a matter of opinion.

Crossref API Rules

6 rules · 4 warnings

SPECTRAL

Crossref API Rules

6 rules · 5 errors · 1 warnings

SPECTRAL

JSON Schema 1

Standalone JSON Schema definitions describe the data models behind the API. We profile them so the shapes are validatable on their own — useful long after a single request is forgotten.

Standalone JSON Schema definitions for this provider's data models.

Crossref Work

38 properties

JSON SCHEMA

Security Posture 2

Authentication, domain security, vulnerability disclosure, and trust-center signals — the evidence that a provider takes security seriously enough to document it. We profile it because you can't govern what you can't see.

Authentication, domain security, vulnerability disclosure, and trust-center signals.

Crossref Domain Security

TLSv1.3 · DMARC

SECURITY

Crossref Vulnerability Disclosure

security.txt · contact published

SECURITY

Agentic Access 1

An x-agentic-access contract marks which operations are safe for an agent to run on its own and which need a human in the loop. It is the difference between an API an agent can use and one it can use safely.

Recommended x-agentic-access execution contracts for AI agents.

Crossref Agentic Access

18 operations

18 operations · 0 acting

AGENTIC

Resources

Every other property we hold for Crossref — documentation, portals, status pages, policies, and corporate surface — grouped by the job it does, following the integrator's arc from getting started to running in production.

Documentation 3

Reference material describing how the API behaves

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

Design & Contract 2

Pagination, idempotency, versioning, errors, and events

Build 1

SDKs, sample code, and the tooling you integrate with

Access & Security 2

Authentication, authorization, and security posture

Operate 2

Status, limits, changes, and where to get help

Commercial 1

Pricing, plans, and the legal terms of use

Company 3

The organization behind the API

← All providers · Data indexed from github.com/api-evangelist/crossref · machine-readable index on apis.io