1330 Thirukkural poems and explanation in Tamil and English.
Thirukkural API is a free Books API that requires no API key, is served over HTTPS and supports CORS, so it can be called from the browser.
Details from api-thirukkural.web.app.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
Full-text + semantic search across the Urantia Papers, with audio narration, entities, translations
Free REST API for the Runyankore-Rukiga Bible — 66 books, 31106 verses
The Thirukkural API is provided by API THIRUKKURAL (api-thirukkural.web.app).
Yes. The Thirukkural API is listed in the Books category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The Thirukkural API requires no authentication, so you can start making requests without signing up.
Yes. The Thirukkural API supports CORS, so front-end JavaScript can call it directly.
Yes. The Thirukkural API is served over HTTPS, so it's safe to use in production.