# External APIs

## Open Library API

- **Purpose:** Search for books by title, author, or ISBN to populate book metadata
- **Documentation:** https://openlibrary.org/dev/docs/api/search
- **Base URL(s):** https://openlibrary.org
- **Authentication:** None (public API, no API key required)
- **Rate Limits:** ~100 requests per 5 minutes (unofficial limit, respect fair use)

**Key Endpoints Used:**
- `GET /search.json?q={query}` - Search for books by keyword, returns title, author, pages, cover IDs

**Cover Images:**
- Base URL: `https://covers.openlibrary.org/b/id/{cover_id}-{size}.jpg`
- Sizes: S (small), M (medium), L (large)
- Example: `https://covers.openlibrary.org/b/id/8233808-M.jpg`

**Integration Notes:**
- Cache search results for 1 hour to reduce API calls
- Implement exponential backoff if rate limited (429 response)
- Fallback to manual entry if API unavailable
- Extract `number_of_pages_median` or first `number_of_pages` value for total pages
- Some books may not have cover images (use placeholder)
- Consider Google Books API as backup if Open Library quality is insufficient

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