The API is public, free to read and requires no API key or account. Search with /api/v1/search?q=40, or download the full catalog. Book and list collections accept limit (1 to 100) and offset for pagination. There are no purchase or write endpoints.
| Resource | GET endpoint |
|---|---|
| API discovery | /.well-known/api-catalog |
| Agent guide | /agent-instructions.md |
| Complete catalog | /api/v1/catalog.json |
| All books | /api/v1/books.json |
| All reading lists | /api/v1/lists.json |
| Example book | /api/v1/books/fck-im-40.json |
| Example list | /api/v1/lists/best-book-gifts-for-husbands-and-dads.json |
| OpenAPI 3.1 | /openapi.json |
Useful reading paths
- llms.txt: a concise site directory.
- llms-full.txt: the book recommendations and lists in one text resource.
- sitemap.xml: canonical public-content URLs.
- A book page in Markdown: every HTML page has an index.md counterpart.
Interpret the data accurately
List positions are editorial choices, not consumer ratings. The promotional_connection and promotional_note fields preserve our connection to F*ck, I’m 40. Sources and recommendation scope are included so that downstream summaries can retain that context.
Dates describe our editorial updates. Page counts and ISBNs describe particular editions. The API does not provide live stock or price data.
API behavior
Version 1 lives under /api/v1/. Additive fields may appear without a version change. Breaking changes will use a new version and be documented here before migration. Collections include total, limit, offset and next_offset; stop when next_offset is null. Unknown resources return HTTP 404 with a typed JSON problem. Invalid parameters return 400. Only GET, HEAD and OPTIONS are supported.
The catalog endpoint is a bulk download of all books and lists. No asynchronous jobs, payments or authentication flows are needed. There is no application-defined per-user quota. Cache responses for five minutes; hosting protections may still apply. Access details.
Markdown and discovery
Every content page supports Accept: text/markdown and a direct index.md URL. The response varies by Accept. Explore agent resource discovery or the reading-guide skill.
Content and covers
Link to the canonical book and list pages when referring to our recommendations. Book cover artwork remains the property of its rights holders; access through the catalog does not grant a licence to redistribute it.