Gutendex

Gutendex is a simple, self-hosted JSON-based web API for serving book catalog information from Project Gutenberg, providing structured metadata for over 70,000 free ebooks including titles, authors, subjects, bookshelves, languages, copyright status, media types, downloadable formats, and download counts. The hosted instance at gutendex.com runs the open-source Django project by Gareth B. Johnson under the MIT license.

Gutendex publishes 1 API contract indexed on the APIs.io network: Books API. Tagged areas include Books, Catalog, Ebooks, Library, and Literature.

The Gutendex catalog on APIs.io includes 1 JSON-LD context and 2 Spectral governance rulesets.

Gutendex’s developer surface includes documentation, pricing, authentication, getting-started guide, tooling, and 16 more developer resources.

🌐 Visit website 📡 Profile data on GitHub

35.6/100 thin ▬ flat Agent 31/100 agent aware Front door AI 1/6 silent open core · MIT Full breakdown ↓
scored 2026-11-06 · rubric v0.27.0 · Show this score on your site →

AccessFreeOpen

1 published contract 8 Features 6 Use Cases

Books Catalog Ebooks Library Literature Metadata Open SourceProject GutenbergPublic APIs Public Domain

Kin Score

Kin Score How this is scored →
scored 2026-11-06 · rubric v0.27.0

Composite quality — 35.6/100 · thin

Contract Quality 13.4 / 21

Developer Ergonomics 5.7 / 17

Access Clarity 2.7 / 17

Operational Transparency 1.5 / 11

Contract Governance 2.4 / 10

Discoverability 4.9 / 9

Regulatory Posture 2.5 / 15

Agent readiness — 31/100 · 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

Pagination 5 / 5

Distinct Operations 3 / 3

MCP Tool Quality 6 / 6

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/.

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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
Stable Error Semantics +8 pts — OpenAPI $refs a shared error schema across 4xx/5xx responses (verified), else common[].type includes ErrorCatalog / ErrorCodes / DeclineCodes
A2A Agent Card +8 pts — a2a/-a2a.yml manifest, graded on conformance.grade against A2A 1.0.0
Registration Without a Human +6 pts — a `registration_endpoint` in the served RFC 8414 / OIDC discovery document
Delegated User Identity +6 pts — a served discovery document listing authorization_code in grant_types_supported (served), else an oauth2 authorizationCode flow or openIdConnect declared in an OpenAPI (documented)
Typed Event Surface +6 pts — AsyncAPI document, OR webhooks/callbacks objects in the as-published OpenAPI, OR common[].type includes Webhooks

5 more unmet checks in the Agent Readiness table above.

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

Access Clarity scores 15.8 — up to +16.8 composite points
Developer Ergonomics scores 33.3 — up to +13.3 composite points
Operational Transparency scores 13.2 — up to +11.3 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/gutendex/apis.yml: open an issue on github.com/api-evangelist/gutendex 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 →

Markets this provider is in provisional

The Kin Score Market layer reads a provider inside its market: its position, and how deep its integrations go. Depth is only comparable within a position. Provisional and unweighted: not part of the Kin Score or agent readiness.

Market	Position	Depth	Registered MCP server	Declares compatibility
Book Publishing (ONIX / ISBN / EPUB supply chain)	long-tail	5.0 (thin)	-	-

Registered MCP server and declares compatibility are report only — not weighted. Undeclared means we found nothing we can read, so there is no number: we never infer integrations.

Standards implemented 1

Standards this provider implements or carries. De facto ones are profiled and measured by the API Commons; formal ones come from the standards directory and are linked by the provider's own tags. The evidence column says how each claim was established — not that it was made.

OpenAPI

measured — observed by APIs.io (published)

APIs 1

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

Gutendex Books API

Query and retrieve metadata for Project Gutenberg ebooks.

Open Collections 2

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

Gutendex API

OPEN COLLECTION

Gutendex Books API

OPEN COLLECTION

Gutendex API pricing

Not yet checked against Gutendex's own pricing page. Compiled by API Evangelist on 2026-05-29 from gutendex.com; confirm before you rely on a figure. A free plan or tier is listed.

Plan	Price
Free Hosted free	Free
Self-Hosted open-source	Free

Plan details, limits and sources →

Rate limits

Results per page: 32 items per page
Search terms per query: 32 tokens per request
Hosted instance request rate: unlimited undocumented

Compiled by API Evangelist, not yet checked against Gutendex's documentation. Rate-limit details →

Pricing Plans 1

Published pricing tiers and plan structures.

Gutendex Plans Pricing

2 plans

PLANS

Rate Limits 1

Documented rate limits and quota policies.

Gutendex Rate Limits

3 limits

RATE LIMITS

Service Levels 1

Uptime the provider promises or reports, as SLA4OAI. Read from its own pages; APIs.io runs no monitors.

Gutendex

SLA

Features 8

Notable capabilities this provider offers.

Free Public API

No API key, no signup, no rate limit documented; gutendex.com is openly available.

70,000+ Ebook Catalog

Mirrors the full Project Gutenberg catalog of free public-domain ebooks.

Rich Filtering

Filter by author birth/death year, copyright status, language, MIME type, IDs, search keywords, and topic.

Multiple Sort Orders

Sort results by popularity (default), ascending ID, or descending ID.

Multi-format Downloads

Each book exposes a Format object mapping MIME types (HTML, EPUB, MOBI, plain text, JPEG) to direct download URLs.

Bookshelves and Subjects

Books are tagged with Library of Congress subject headings and curated Project Gutenberg bookshelves.

Multi-language Support

Books are indexed by two-character ISO language codes; filter by multiple languages at once.

Self-Hostable

MIT-licensed Django app that operators can run on their own infrastructure with nightly Project Gutenberg catalog sync.

Scroll for all 8

Semantic Vocabularies 1

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

Gutendex Context

12 classes · 12 properties

JSON-LD

Spectral Rules 2

Spectral governance rulesets for linting and validating these APIs.

Gutendex — jsonschema rules

5 rules · 4 warnings 1 info

SPECTRAL

Gutendex API Rules

13 rules · 8 errors 4 warnings 1 info

SPECTRAL

JSON Schema 5

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

BookList

4 properties

JSON SCHEMA

Book

13 properties

JSON SCHEMA

Error

1 properties

JSON SCHEMA

Format

0 properties

JSON SCHEMA

Person

3 properties

JSON SCHEMA

JSON Structure 5

JSON Structure definitions describing this provider's data shapes.

Gutendex Book List Structure

4 properties

JSON STRUCTURE

Gutendex Book Structure

13 properties

JSON STRUCTURE

Gutendex Error Structure

1 properties

JSON STRUCTURE

Gutendex Format Structure

0 properties

JSON STRUCTURE

Gutendex Person Structure

3 properties

JSON STRUCTURE

Examples 6

Example request and response payloads for these APIs.

Gutendex Book Example

13 fields

EXAMPLE

Gutendex Error Example

1 fields

EXAMPLE

Gutendex Format Example

6 fields

EXAMPLE

Gutendex Get Book Example

13 fields

EXAMPLE

Gutendex List Books Example

4 fields

EXAMPLE

Gutendex Person Example

3 fields

EXAMPLE

Security Posture 1

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

Gutendex Domain Security

TLSv1.3

SECURITY

Agentic Access 1

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

Gutendex Agentic Access

2 operations

2 operations · 0 acting

AGENTIC

Use Cases 6

What developers build with this provider.

Literature Analytics

Power large-scale analysis of public-domain literature by ingesting the structured Project Gutenberg catalog.

Educational Apps

Build classroom or self-study apps that surface public-domain texts by subject, author, or reading level.

Reading Recommendation Engines

Use the download_count and bookshelf data to recommend popular classics or themed reading lists.

Digital Library Backends

Power library catalog interfaces and ebook reader apps with a clean JSON facade over Project Gutenberg's XML archives.

Natural Language Processing Datasets

Use the catalog to discover bulk text downloads for training language models on public-domain corpora.

Citation and Reference Tools

Power author/title lookup widgets in citation managers and academic writing tools.

Integrations 4

Pre-built integrations with other platforms and tools.

Project Gutenberg

Upstream source. Gutendex nightly-ingests the official Project Gutenberg XML catalog and republishes it as JSON.

Django REST Framework

Built on Django + Django REST Framework. Operators can extend the API with additional viewsets.

Model Context Protocol

Community-maintained MCP servers expose Project Gutenberg / Gutendex to LLM agents (bobbyhouse, vellankis-space, nasimcoderex).

PostgreSQL / SQLite

Default Django storage backends used by self-hosted instances for catalog persistence.

Resources

Get Started 1

Portal, sign-up, and the first successful call

GettingStarted

GettingStarted

Documentation 3

Reference material describing how the API behaves

Documentation

Documentation

OpenAPI

OpenAPI

JSONSchema

JSONSchema

Agent Surfaces 1

MCP servers, agent skills, and machine-readable catalogs

AgenticAccess

AgenticAccess

Design & Contract 3

Pagination, idempotency, versioning, errors, and events

JSONLD

JSONLD

SpectralRules

SpectralRules

Vocabulary

Vocabulary

Build 4

SDKs, sample code, and the tooling you integrate with

GitHubRepository

GitHubRepository

Project Gutenberg MCP Server (bobbyhouse)

Tools

Project Gutenberg MCP Server (vellankis-space)

Tools

Gutenberg MCP Server (nasimcoderex)

Tools

Access & Security 2

Authentication, authorization, and security posture

DomainSecurity

DomainSecurity

Authentication

Authentication

Operate 2

Status, limits, changes, and where to get help

IssueTracker

IssueTracker

RateLimits

RateLimits

Commercial 3

Pricing, plans, and the legal terms of use

License

License

Plans

Plans

Pricing

Pricing

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: gutendex
name: Gutendex
description: Gutendex is a simple, self-hosted JSON-based web API for serving book catalog information from Project Gutenberg,
  providing structured metadata for over 70,000 free ebooks including titles, authors, subjects, bookshelves, languages, copyright
  status, media types, downloadable formats, and download counts. The hosted instance at gutendex.com runs the open-source
  Django project by Gareth B. Johnson under the MIT license.
deliveryModel:
  model: open-core
  license: MIT
  open_source: true
  commercial: true
  callable_host: true
  label: Open core · an OSS project plus a commercial hosted product
  confidence: high
  source:
  - license
  - openapi
  - pricing
  generated: '2026-08-28'
  method: derived
accessModel:
  pricing: free
  onboarding: open
  trial: false
  try_now: false
  public: false
  gated: none
  gated_source:
  - onboarding
  label: Free · Open access
  confidence: low
  try_now_blocked_by: 'probed-unreachable: the enrichment probe recorded no reachable surface'
  probe_state: probed-unreachable
  source:
  - plans
  - security
  generated: '2026-11-06'
  method: derived
image: https://gutendex.com/static/images/gutendex.png
url: https://raw.githubusercontent.com/api-evangelist/gutendex/main/apis.yml
created: '2026-05-28'
modified: '2026-05-29'
specificationVersion: '0.23'
type: Index
access: 3rd-Party
x-type: opensource
x-category: Books
x-coverage:
  state: probed-unreachable
  probed: '2026-09-03'
  evidence:
  - url: https://gutendex.com/
    status: 403
    note: 'cf-mitigated: challenge'
  - url: https://gutendex.com/books/
    status: 403
    note: 'cf-mitigated: challenge'
  - url: https://gutendex.com/books/1
    status: 403
    note: 'cf-mitigated: challenge'
  - url: https://gutendex.com/zzz-control-26366
    status: 403
    note: invented control path, also challenged -- the wall is host-wide, not per-route
  - url: https://gutendex.com/robots.txt
    status: 200
    note: 'wildcard Disallow: /books/; named bans on ClaudeBot, GPTBot, CCBot, Bytespider, Amazonbot, Applebot-Extended, Google-Extended,
      meta-externalagent; Content-Signal ai-train=no'
x-source: public-apis/public-apis
x-tier: 3
x-tier-reason: bulk-registered-from-public-apis
tags:
- Books
- Catalog
- Ebooks
- Library
- Literature
- Metadata
- Open Source
- Project Gutenberg
- Public APIs
- Public Domain
tags_raw:
- Books
- Catalog
- Ebooks
- Library
- Literature
- Metadata
- Open Source
- Project Gutenberg
- Public APIs
- Public Domain
- Open-Source
apis:
- aid: gutendex:gutendex-books-api
  name: Gutendex Books API
  description: Query and retrieve metadata for Project Gutenberg ebooks.
  humanURL: https://gutendex.com
  tags:
  - Books
  properties:
  - type: OpenAPI
    url: openapi/gutendex-books-api-openapi.yml
  - type: Documentation
    url: https://gutendex.com
  - type: JSONSchema
    url: json-schema/gutendex-book-schema.json
  - type: JSONSchema
    url: json-schema/gutendex-book-list-schema.json
  - type: JSONSchema
    url: json-schema/gutendex-person-schema.json
  - type: JSONSchema
    url: json-schema/gutendex-format-schema.json
  - type: JSONSchema
    url: json-schema/gutendex-error-schema.json
  - type: JSONLD
    url: json-ld/gutendex-context.jsonld
common:
- type: IssueTracker
  url: https://github.com/garethbjohnson/gutendex/issues
- type: License
  name: MIT
  url: https://github.com/garethbjohnson/gutendex/blob/master/LICENSE
- type: AgenticAccess
  url: agentic-access/gutendex-agentic-access.yml
- type: DomainSecurity
  url: security/gutendex-domain-security.yml
- type: Website
  url: https://gutendex.com
- type: Documentation
  url: https://gutendex.com
- type: OpenAPI
  url: openapi/_original/gutendex-api-openapi.yml
- type: JSONSchema
  url: json-schema/gutendex-book-schema.json
- type: JSONLD
  url: json-ld/gutendex-context.jsonld
- type: GitHubRepository
  url: https://github.com/garethbjohnson/gutendex
- type: PublicAPIsListing
  url: https://github.com/public-apis/public-apis
- type: Plans
  url: plans/gutendex-plans-pricing.yml
- type: Pricing
  url: plans/gutendex-plans-pricing.yml
- type: RateLimits
  url: rate-limits/gutendex-rate-limits.yml
- type: SpectralRules
  url: rules/gutendex-rules.yml
- type: Vocabulary
  url: vocabulary/gutendex-vocabulary.yml
- type: Authentication
  url: https://gutendex.com
  description: No authentication required; the hosted instance is publicly accessible.
- type: GettingStarted
  url: https://github.com/garethbjohnson/gutendex/wiki/Installation-Guide
- type: Tools
  title: Project Gutenberg MCP Server (bobbyhouse)
  url: https://github.com/bobbyhouse/project-gutenberg-mcp
- type: Tools
  title: Project Gutenberg MCP Server (vellankis-space)
  url: https://github.com/vellankis-space/project-gutenberg-mcp-server
- type: Tools
  title: Gutenberg MCP Server (nasimcoderex)
  url: https://github.com/nasimcoderex/gutenberg-mcp-server
- type: Features
  data:
  - name: Free Public API
    description: No API key, no signup, no rate limit documented; gutendex.com is openly available.
  - name: 70,000+ Ebook Catalog
    description: Mirrors the full Project Gutenberg catalog of free public-domain ebooks.
  - name: Rich Filtering
    description: Filter by author birth/death year, copyright status, language, MIME type, IDs, search keywords, and topic.
  - name: Multiple Sort Orders
    description: Sort results by popularity (default), ascending ID, or descending ID.
  - name: Multi-format Downloads
    description: Each book exposes a Format object mapping MIME types (HTML, EPUB, MOBI, plain text, JPEG) to direct download
      URLs.
  - name: Bookshelves and Subjects
    description: Books are tagged with Library of Congress subject headings and curated Project Gutenberg bookshelves.
  - name: Multi-language Support
    description: Books are indexed by two-character ISO language codes; filter by multiple languages at once.
  - name: Self-Hostable
    description: MIT-licensed Django app that operators can run on their own infrastructure with nightly Project Gutenberg
      catalog sync.
- type: UseCases
  data:
  - name: Literature Analytics
    description: Power large-scale analysis of public-domain literature by ingesting the structured Project Gutenberg catalog.
  - name: Educational Apps
    description: Build classroom or self-study apps that surface public-domain texts by subject, author, or reading level.
  - name: Reading Recommendation Engines
    description: Use the download_count and bookshelf data to recommend popular classics or themed reading lists.
  - name: Digital Library Backends
    description: Power library catalog interfaces and ebook reader apps with a clean JSON facade over Project Gutenberg's
      XML archives.
  - name: Natural Language Processing Datasets
    description: Use the catalog to discover bulk text downloads for training language models on public-domain corpora.
  - name: Citation and Reference Tools
    description: Power author/title lookup widgets in citation managers and academic writing tools.
- type: Integrations
  data:
  - name: Project Gutenberg
    description: Upstream source. Gutendex nightly-ingests the official Project Gutenberg XML catalog and republishes it as
      JSON.
  - name: Django REST Framework
    description: Built on Django + Django REST Framework. Operators can extend the API with additional viewsets.
  - name: Model Context Protocol
    description: Community-maintained MCP servers expose Project Gutenberg / Gutendex to LLM agents (bobbyhouse, vellankis-space,
      nasimcoderex).
  - name: PostgreSQL / SQLite
    description: Default Django storage backends used by self-hosted instances for catalog persistence.
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
  url: https://apievangelist.com

Gutendex API — frequently asked questions

Does Gutendex have an API?

Yes. APIs.io lists 1 API from Gutendex, including Gutendex Books API.

Is there an OpenAPI specification for the Gutendex API?

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

How do I authenticate with the Gutendex API?

Gutendex uses bearer-token authentication.

How much does the Gutendex API cost?

APIs.io lists 2 pricing plans for Gutendex, with each plan's price, limits and inclusions under Pricing on this page.

Is the Gutendex API ready for AI agents?

Gutendex has a Kin Score of 35.6 out of 100 (thin) and an Agent Readiness score of 31.2 (agent-aware), scored by API Evangelist on 2026-11-06.

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