Hardcover

Hardcover is a social discovery platform for serious book lovers, offering a mobile app and web experience where users can track, share, and explore books. The service lets readers build personal libraries, follow others, discover new reads, and engage with community features such as Discord, blog posts, and public roadmaps. Hardcover provides a GraphQL API for developers to access book data, user progress, and community content, documented at docs.hardcover.app with guides, reference, and SDKs.

Hardcover is listed with 2 APIs on the APIs.io network. Tagged areas include Company, Social, Book, Reading, and Community.

The Hardcover catalog on APIs.io includes 1 JSON-LD context and 1 Spectral governance ruleset.

Hardcover’s developer surface includes authentication, changelog, documentation, API reference, getting-started guide, support, engineering blog, and 21 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

37.3/100 thin Agent 31/100 agent ready Full breakdown ↓
scored 2026-10-31 · rubric v0.25.0 · Show this score on your site →

2 APIs

Company Social Book Reading CommunityAPI

Kin Score

Kin Score How this is scored →
scored 2026-10-31 · rubric v0.25.0

Composite quality — 37.3/100 · thin

Contract Quality 3.8 / 21

Developer Ergonomics 12.0 / 17

Access Clarity 0.0 / 17

Operational Transparency 5.8 / 11

Contract Governance 2.2 / 10

Discoverability 5.6 / 9

Regulatory Posture 4.9 / 15

Agent readiness — 31/100 · agent ready

Machine-Readable Contract 18 / 18

Agentic Access Contract 0 / 10

Documented Reversibility 0 / 6

MCP Server 0 / 12

Machine-Readable Auth 10 / 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 5 / 5

Well-Known Catalog 0 / 4

Consent & Bot Identity 0 / 3

A2A Agent Card 0 / 8

Dry-Run / Simulate Mode 0 / 4

Delegated User Identity 6 / 6

Protected Resource Metadata 0 / 5

Registration Without a Human 0 / 6

Agentic Commerce Well-Known Document 0 / 5

Pagination 5 / 5

Distinct Operations 3 / 3

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

MCP Server +12 pts — deployment.mode + probe verdict on the mcp/ manifest, not the pointer; an unprobed slug falls back to authorship
Agentic Access Contract +10 pts — agentic_access artifact present (x-agentic-access), graded by author
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)
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
Request/Response Examples +7 pts — share of operations carrying request/response examples; else an Examples / Code Samples link

8 more unmet checks in the Agent Readiness table above.

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

Contract Quality scores 17.8 — up to +20.6 composite points
Access Clarity scores 0.0 — up to +20.0 composite points
Contract Governance scores 22.0 — up to +9.4 composite points

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.

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/hardcover/apis.yml: open an issue on github.com/api-evangelist/hardcover 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 2

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

Hardcover GraphQL API

GraphQL API for accessing book data, user progress, and community content.

Hardcover API

Hardcover API as documented publicly: 4 operations. Contract generated from the documentation by API Evangelist (2026-10-28); not the provider's own document.

Rate Limits 1

Documented rate limits and quota policies.

Hardcover Rate Limits

0 limits

RATE LIMITS

Semantic Vocabularies 1

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

Hardcover Context

1 classes · 6 properties

JSON-LD

Spectral Rules 1

Spectral governance rulesets for linting and validating these APIs.

Hardcover API Rules

11 rules · 9 errors 1 warnings 1 info

SPECTRAL

JSON Schema 1

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

PostOauth2DeviceResponse

6 properties

JSON SCHEMA

Security Posture 3

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

Hardcover Authentication

2 schemes

SECURITY

Hardcover Domain Security

TLSv1.3 · HSTS · DMARC

SECURITY

Hardcover Vulnerability Disclosure

security.txt · contact published

SECURITY

Scopes 1

OAuth scopes governing access to this provider's APIs.

Hardcover Scopes

OAuth 2.0 · no documented scopes

0 scopes

SCOPES

Resources

Get Started 2

Portal, sign-up, and the first successful call

DeveloperPortal

DeveloperPortal

GettingStarted

GettingStarted

Documentation 2

Reference material describing how the API behaves

Documentation

Documentation

APIReference

APIReference

Agent Surfaces 2

MCP servers, agent skills, and machine-readable catalogs

AgentSkill

AgentSkill

WellKnown

WellKnown

Design & Contract 5

Pagination, idempotency, versioning, errors, and events

Spectral

JSONLD

Vocabulary

DataModel

Conformance

Build 3

SDKs, sample code, and the tooling you integrate with

SDKs

SDKs

Packages

Packages

GitHubOrganization

GitHubOrganization

Access & Security 6

Authentication, authorization, and security posture

Security

Authentication

SecurityTxt

SecurityTxt

VulnerabilityDisclosure

VulnerabilityDisclosure

DomainSecurity

DomainSecurity

Operate 4

Status, limits, changes, and where to get help

StatusPage

ChangeLog

Support

Roadmap

Company 2

The organization behind the API

Website

Website

Blog

Blog

Other 2

Properties that don't map to a standard resource type

Hosts

Hosts

Vendors

Vendors

Source (apis.yml)

aid: hardcover
name: Hardcover
description: Hardcover is a social discovery platform for serious book lovers, offering a mobile app and web experience where
  users can track, share, and explore books. The service lets readers build personal libraries, follow others, discover new
  reads, and engage with community features such as Discord, blog posts, and public roadmaps. Hardcover provides a GraphQL
  API for developers to access book data, user progress, and community content, documented at docs.hardcover.app with guides,
  reference, and SDKs.
url: https://artifacts.apis.io/hardcover/apis.yml
x-type: company
x-source: harvest:new-submission
x-tier: profiled
x-tier-reason: enrichment pass 2026-10-28 (modular-v1; was harvest)
specificationVersion: '0.20'
created: '2026-10-28'
modified: '2026-10-28'
tags:
- Company
- Social
- Book
- Reading
- Community
- API
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
- FN: APIs.json
  email: info@apis.io
image: https://hardcover.app/favicon.ico
common:
- type: Spectral
  url: rules/hardcover-rules.yml
- type: JSONLD
  url: json-ld/hardcover-context.jsonld
- type: Vocabulary
  url: vocabulary/hardcover-vocabulary.yml
- type: AgentSkill
  url: skills/_index.yml
- type: DataModel
  url: data-model/hardcover-data-model.yml
- type: Security
  url: https://hardcover.app/pages/policies
- type: Authentication
  url: authentication/hardcover-authentication.yml
- type: Conformance
  url: conformance/hardcover-conformance.yml
- type: SecurityTxt
  url: well-known/hardcover-security.txt
- type: SecurityTxt
  url: well-known/hardcover-dev-security.txt
- type: WellKnown
  url: well-known/hardcover-well-known.yml
- type: Hosts
  url: hosts/hardcover-hosts.yml
- type: Vendors
  url: vendors/hardcover-vendors.yml
- type: SDKs
  url: packages/hardcover-packages.yml
- type: Packages
  url: packages/hardcover-packages.yml
- type: StatusPage
  url: https://status.hardcover.app/
- type: ChangeLog
  url: https://docs.hardcover.app/sdk/typescript/changelog/
- type: VulnerabilityDisclosure
  url: security/hardcover-vulnerability-disclosure.yml
- type: DomainSecurity
  url: security/hardcover-domain-security.yml
- type: Website
  url: https://hardcover.app/
- type: DeveloperPortal
  url: https://docs.hardcover.app/
- type: Documentation
  url: https://docs.hardcover.app/
- type: APIReference
  url: https://docs.hardcover.app/api/graphql/schemas
- type: GettingStarted
  url: https://docs.hardcover.app/api/getting-started/
- type: Support
  url: https://hardcover.app/pages/support
- type: Blog
  url: https://hardcover.app/blog
- type: GitHubOrganization
  url: https://github.com/hardcoverapp/hardcover-docs/
- type: Roadmap
  url: https://roadmap.hardcover.app/
apis:
- name: Hardcover GraphQL API
  description: GraphQL API for accessing book data, user progress, and community content.
  humanURL: https://docs.hardcover.app/api/graphql/schemas
  baseURL: https://docs.hardcover.app/api/graphql
  aid: hardcover:hardcover-graphql-api
- aid: hardcover:hardcover-api
  name: Hardcover API
  description: 'Hardcover API as documented publicly: 4 operations. Contract generated from the documentation by API Evangelist
    (2026-10-28);

    not the provider''s own document.'
  humanURL: https://docs.hardcover.app/api/oauth
  baseURL: https://api.hardcover.app
  properties:
  - type: OpenAPI
    url: openapi/_ae-authored/hardcover-openapi-generated.yml
    x-provenance: generated
  - type: JSONSchema
    url: json-schema/hardcover-post-oauth2-device-response-schema.json
x-submission-probe: 403, 2026-10-26
x-coverage:
  state: unreadable
  reason: no-machine-readable-spec
  detail: Documentation is publicly available but no machine‑readable contract (OpenAPI, GraphQL SDL, AsyncAPI, gRPC, or WSDL)
    could be retrieved.
  evidence:
  - url: https://docs.hardcover.app/api/graphql/schemas
    status: 200
  checked: '2026-10-28'
x-enrichment:
  date: '2026-10-28'
  status: enriched
  artifacts_added: 28
  pass: modular-v1
  engine: identity=oss,contract=oss,surfaces=oss,docs=oss,regulatory=oss

Hardcover API — frequently asked questions

Does Hardcover have an API?

Yes. APIs.io lists 2 APIs from Hardcover, including Hardcover GraphQL API and Hardcover API.

Is there an OpenAPI specification for the Hardcover API?

Yes. APIs.io indexes 1 OpenAPI specification for Hardcover, each linked for download from this page.

How do I authenticate with the Hardcover API?

Hardcover documents its authentication (2 schemes). The details are profiled on APIs.io as Hardcover Authentication.

Is the Hardcover API ready for AI agents?

Hardcover has a Kin Score of 37.3 out of 100 (thin) and an Agent Readiness score of 31.0 (agent-ready), scored by API Evangelist on 2026-10-31.

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