loc-catalog

# Library of Congress API Skill Search and retrieve items from LOC's digitized collections — books, photos, maps, manuscripts, newspapers, audio, and more. ## Critical: Things Claude Won't Know Without This Skill ### This API covers digitized collections, NOT the full library catalog The loc.gov JSON API searches LOC's **digitized and online collections** — not the full OPAC. By default, only digitized items are returned. Add `all=true` to include non-digitized catalog records. ### JSON requires `fo=json` parameter, NOT a URL extension Unlike LibraryCloud (`.json` extension), LOC uses a query parameter: ``` CORRECT: https://www.loc.gov/search/?q=hamlet&fo=json WRONG: https://www.loc.gov/search.json?q=hamlet ``` ### Facet filters use `fa=` with pipe separators ``` Single: ?fa=subject:physics Multiple: ?fa=subject:wildlife|location:yellowstone ``` Available facet fields: `subject`, `contributor`, `location`, `language`, `original-format`, `online-format`, `partof`, `digitized`, `access-restricted`. ### Format-specific endpoints are shortcuts `/books/`, `/photos/`, `/maps/`, `/audio/`, `/newspapers/`, `/manuscripts/`, `/film-and-videos/`, `/notated-music/` all accept the same params as `/search/`. ## Key Search Parameters | Param | Description | Example | |-------|-------------|---------| | `q` | Keyword search | `q=hamlet+shakespeare` | | `fa` | Facet filter | `fa=subject:physics\|language:english` | | `dates` | Date range (YYYY/YYYY) | `dates=1920/1940` | | `c` | Results per page (25, 50, 100, 150) | `c=50` | | `sp` | Page number (starts at 1) | `sp=2` | | `sb` | Sort: `date`, `date_desc`, `title_s`, `title_s_desc` | `sb=date_desc` | | `all` | Include non-digitized (`true`/`false`) | `all=true` | | `at` | Select attributes (comma-sep) | `at=item,resources` | | `fo` | Format: `json` or `yaml` | `fo=json` | ## Item Lookup by LCCN/ID ``` https://www.loc.gov/item/{LCCN}/?fo=json ``` Returns full item detail including `cite_this` (APA/Chicago/MLA citations), `resources` (download links), `other_formats` (MARCXML, MODS, Dublin Core). ## Response Structure ### Search Results ```json { "results": [ { "id": "http://www.loc.gov/item/95521789/", "title": "Item title", "date": "1796-01-01", "contributor": ["Name"], "subject": ["Subject term"], "language": ["English"], "original_format": ["book"], "description": ["..."], "image_url": ["//tile.loc.gov/..."], "digitized": true, "number_lccn": ["95521789"] } ], "pagination": { "of": 85604, "total": 17121, "perpage": 5, "current": 1 }, "facets": { ... } } ``` ### Item Detail The `item` object adds: `call_number`, `created_published`, `rights`, `summary`, `stmt_of_responsibility`, `genre`, and `cite_this` with pre-formatted citations. ## Python Script ```python from scripts.loc_api import LocAPI loc = LocAPI() # Keyword search results = loc.search("hamlet shakespeare", limit=10) # Format-specific photos = loc.search("civil war", format="photos", dates="1860/1865") # Faceted search results = loc.search("wildlife", facets={"subject": "birds", "location": "yellowstone"}) # Item lookup item = loc.get_item("95521789") citation = loc.get_citation(item, style="apa") # Browse collections collections = loc.list_collections() items = loc.browse_collection("civil-war-maps", limit=20) # Summarize for r in results[:5]: print(loc.summarize(r)) ``` ## Pagination - Max 150 results per page (`c=150`) - Hard limit: cannot paginate past 100,000th result - Use facets/date ranges to narrow large result sets ## API Etiquette - No authentication required - Rate limiting is enforced (exact limits unpublished) — add 0.5-1s between requests - Include a User-Agent header ## Related Skills - **harvard-library-catalog**: Cross-reference Harvard holdings with LOC items - **hathitrust-catalog**: Use LCCNs from LOC to check HathiTrust for digital full-text - **wikidata-search**: LOC authority IDs (P244) link Wikidata entities to LOC records ## Resources - `references/api_reference.md` — Complete parameter and response field reference - `scripts/loc_api.py` — Python client with search, item lookup, collection browsing, and citation extraction