ISBN citation API

One ISBN request returns all five citation styles and the available bibliographic details.

One ISBN, five styles

Request JSON explicitly to receive MLA, APA, Chicago, Wikipedia, and BibTeX citations, normalized ISBN identity, available book details, and available quality and uncertainty fields.

curl -H 'Accept: application/json' https://www.ottobib.com/isbn/9780226458113
curl https://www.ottobib.com/isbn/9780226458113.json
curl https://www.ottobib.com/isbn/9780226458113/bibtex.json

Try the all-style JSON example or the single-style example. Style IDs are mla, apa, chicago, wp, and bibtex.

Handle results honestly

200 with found:true contains the available prepared citation. Fields may be absent or uncertain; a successful response is not a guarantee that every bibliographic detail is known. Review the quality fields and the edition.

200 with found:false is terminal for the immediate lookup attempt. Do not loop on that result. Invalid input returns 400. Rate limiting returns 429; temporary failures return 503. Follow the supplied Retry-After guidance when it is present.

Access and limits

The current public API is free and requires no API key. The default request limit is 50 requests per second with a burst of 100, shared across requests from a client and configurable by deployment. Space requests out and handle rate limiting instead of retrying immediately.

Both normal and ?lookup=local requests read the immutable local publication. A public miss does not synchronously query external catalogues. Routes under /isbn/ are answered in place, including ISBN-10 and explicit .json URLs.

Discovery and integration

• OpenAPI specification: response schemas, operation IDs, examples, and error handling.
• Agent guidance: lookup and retry semantics.
• Downloadable MCP shim source: a standard-library Go program that runs locally over stdio.

For manual use, start with the book citation generator or the ISBN-to-BibTeX converter.