OpenCitations

OpenCitations is an open science research infrastructure providing free access to scholarly bibliographic and citation data. It offers REST APIs for querying citation networks, DOI-based citation lookups, reference data, and bibliographic metadata from millions of research articles. All data is published under CC0 Public Domain Waiver for unrestricted reuse.

OpenCitations publishes 5 APIs on the APIs.io network, including Authors API, Citations API, Editors API, and 2 more. Tagged areas include Citations, Scholarly, Research, Open Science, and Bibliometrics.

The OpenCitations catalog on APIs.io includes 1 JSON-LD context.

OpenCitations’ developer surface includes authentication and 2 more developer resources.

🌐 Visit website 📡 Source on GitHub

28.3/100 thin ▬ flat Agent 26/100 agent aware Full breakdown ↓
scored 2026-09-14 · rubric v0.22.0

2 APIs

Citations Scholarly Research Open Science Bibliometrics DOI Academic

Kin Score

Kin Score How this is scored →
scored 2026-09-14 · rubric v0.22.0

Composite quality — 28.3/100 · thin

Contract Quality 13.5 / 21

Developer Ergonomics 3.6 / 17

Access Clarity 0.0 / 17

Operational Transparency 0.0 / 11

Contract Governance 0.0 / 10

Discoverability 6.5 / 9

Regulatory Posture 4.7 / 15

Agent readiness — 26/100 · agent aware

Machine-Readable Contract 18 / 18

Agentic Access Contract 10 / 10

Documented Reversibility 6 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 10

Idempotency 9 / 9

Stable Error Semantics 0 / 8

Request/Response Examples 7 / 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

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 4 / 4

Delegated User Identity 0 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Regulatory Posture applies to this provider. Its tags matched the Education & Research 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 does not apply to this provider. The published contracts declare no write operations, and a read-only API cannot create-or-update. The facet is excluded from this provider's denominator entirely — not scored zero. A reference or data API is not deficient for being unable to upsert.

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/.

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 github.com/api-evangelist/opencitations: open an issue to ask a question, or submit a pull request to add artifacts. Submit an artifact on GitHub — free → Manage your own listing — the Influence plan, $499/mo →

APIs 6

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

OpenCitations SPARQL Endpoint

SPARQL endpoints for structured queries against the OpenCitations Meta and Index datasets. Provides access to the full Linked Open Data graph for both bibliographic metadata and...

OpenCitations Authors API

Operations for retrieving works by author

OpenCitations Citations API

Operations for retrieving citation metadata and counts

OpenCitations Editors API

Operations for retrieving works by editor

OpenCitations Metadata API

Operations for retrieving bibliographic metadata

OpenCitations References API

Operations for retrieving outgoing reference data

Open Collections 6

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

API Collection

OPEN COLLECTION

OpenCitations Index REST Authors API

OPEN COLLECTION

OpenCitations Index REST Authors Citations API

OPEN COLLECTION

OpenCitations Index REST Authors Editors API

OPEN COLLECTION

OpenCitations Index REST Authors Metadata API

OPEN COLLECTION

OpenCitations Index REST Authors References API

OPEN COLLECTION

Semantic Vocabularies 1

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

Opencitations Context

24 classes · 13 properties

JSON-LD

Examples 5

Example request and response payloads for these APIs.

Author Works

4 fields

EXAMPLE

Citation By Oci

4 fields

EXAMPLE

Citation Count

4 fields

EXAMPLE

Incoming Citations

5 fields

EXAMPLE

Metadata Lookup

4 fields

EXAMPLE

Security Posture 2

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

Opencitations Authentication

apiKey · 1 scheme

SECURITY

Opencitations Domain Security

TLSv1.3

SECURITY

Agentic Access 1

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

Opencitations Agentic Access

9 operations

9 operations · 0 acting

AGENTIC

Resources

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Authentication

Authentication

Source (apis.yml)

name: OpenCitations
description: OpenCitations is an open science research infrastructure providing free access to scholarly bibliographic and
  citation data. It offers REST APIs for querying citation networks, DOI-based citation lookups, reference data, and bibliographic
  metadata from millions of research articles. All data is published under CC0 Public Domain Waiver for unrestricted reuse.
deliveryModel:
  model: unknown
  open_source: false
  commercial: false
  callable_host: true
  label: Delivery model not determined — needs a product licence on record
  confidence: low
  source:
  - openapi
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: unknown
  onboarding: unknown
  trial: false
  try_now: false
  public: false
  label: Unknown
  confidence: low
  source:
  - authentication
  - security
  generated: '2026-09-03'
  method: derived
image: https://opencitations.net/static/favicon.ico
url: https://opencitations.net
created: '2024-01-01'
modified: '2026-06-13'
specificationVersion: '0.23'
tags:
- Citations
- Scholarly
- Research
- Open Science
- Bibliometrics
- DOI
- Academic
apis:
- name: OpenCitations SPARQL Endpoint
  description: SPARQL endpoints for structured queries against the OpenCitations Meta and Index datasets. Provides access
    to the full Linked Open Data graph for both bibliographic metadata and citation entity data using the SPARQL query language.
  image: https://opencitations.net/static/favicon.ico
  humanURL: https://sparql.opencitations.net
  baseURL: https://sparql.opencitations.net
  tags:
  - SPARQL
  - Linked Open Data
  - RDF
  - Scholarly
  properties:
  - type: Documentation
    url: https://sparql.opencitations.net
  contact:
  - FN: OpenCitations
    email: contact@opencitations.net
    X-website: https://opencitations.net
- aid: opencitations:opencitations-authors-api
  name: OpenCitations Authors API
  description: Operations for retrieving works by author
  humanURL: https://api.opencitations.net/index/v2
  baseURL: https://api.opencitations.net/index/v2
  tags:
  - Authors
  properties:
  - type: OpenAPI
    url: openapi/opencitations-authors-api-openapi.yml
  - type: Documentation
    url: https://api.opencitations.net/index/v2
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/index-api.html
  - type: Documentation
    url: https://api.opencitations.net/meta/v1
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/meta-api.html
- aid: opencitations:opencitations-citations-api
  name: OpenCitations Citations API
  description: Operations for retrieving citation metadata and counts
  humanURL: https://api.opencitations.net/index/v2
  baseURL: https://api.opencitations.net/index/v2
  tags:
  - Citations
  properties:
  - type: OpenAPI
    url: openapi/opencitations-citations-api-openapi.yml
  - type: Documentation
    url: https://api.opencitations.net/index/v2
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/index-api.html
  - type: Documentation
    url: https://api.opencitations.net/meta/v1
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/meta-api.html
- aid: opencitations:opencitations-editors-api
  name: OpenCitations Editors API
  description: Operations for retrieving works by editor
  humanURL: https://api.opencitations.net/index/v2
  baseURL: https://api.opencitations.net/index/v2
  tags:
  - Editors
  properties:
  - type: OpenAPI
    url: openapi/opencitations-editors-api-openapi.yml
  - type: Documentation
    url: https://api.opencitations.net/index/v2
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/index-api.html
  - type: Documentation
    url: https://api.opencitations.net/meta/v1
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/meta-api.html
- aid: opencitations:opencitations-metadata-api
  name: OpenCitations Metadata API
  description: Operations for retrieving bibliographic metadata
  humanURL: https://api.opencitations.net/index/v2
  baseURL: https://api.opencitations.net/index/v2
  tags:
  - Metadata
  properties:
  - type: OpenAPI
    url: openapi/opencitations-metadata-api-openapi.yml
  - type: Documentation
    url: https://api.opencitations.net/index/v2
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/index-api.html
  - type: Documentation
    url: https://api.opencitations.net/meta/v1
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/meta-api.html
- aid: opencitations:opencitations-references-api
  name: OpenCitations References API
  description: Operations for retrieving outgoing reference data
  humanURL: https://api.opencitations.net/index/v2
  baseURL: https://api.opencitations.net/index/v2
  tags:
  - References
  properties:
  - type: OpenAPI
    url: openapi/opencitations-references-api-openapi.yml
  - type: Documentation
    url: https://api.opencitations.net/index/v2
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/index-api.html
  - type: Documentation
    url: https://api.opencitations.net/meta/v1
  - type: RateLimits
    url: https://kinlane.github.io/all/opencitations/rate-limits/meta-api.html
maintainers:
- FN: OpenCitations
  email: contact@opencitations.net
  X-website: https://opencitations.net
common:
- type: AgenticAccess
  url: agentic-access/opencitations-agentic-access.yml
- type: DomainSecurity
  url: security/opencitations-domain-security.yml
- type: Authentication
  url: authentication/opencitations-authentication.yml

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