Harvard Library API Skill

Search and retrieve bibliographic records from Harvard Library's catalog of 13M+ items.

Critical: Things Claude Won't Know Without This Skill

LibraryCloud field-based search uses query parameters, NOT Solr syntax

The Item API uses field names as query parameters — not q=field:value Solr syntax.

CORRECT:   https://api.lib.harvard.edu/v2/items.json?title=hamlet&name=shakespeare
WRONG:     https://api.lib.harvard.edu/v2/items?q=title:hamlet

The q= parameter is for keyword search across all fields. Field-specific search uses dedicated parameters like title=, name=, subject=, identifier=, etc.

JSON requires .json in the URL path

Responses are XML by default. To get JSON, append .json before the query string:

JSON:        https://api.lib.harvard.edu/v2/items.json?title=hamlet
Dublin Core: https://api.lib.harvard.edu/v2/items.dc.json?title=hamlet
Default XML: https://api.lib.harvard.edu/v2/items?title=hamlet

PRESTO is for direct record lookup by HOLLIS ID

PRESTO returns raw MARC, MODS, or Dublin Core for a single record by its HOLLIS number. It complements LibraryCloud when you need the original catalog record:

MARC: https://webservices.lib.harvard.edu/rest/marc/hollis/{HOLLIS_ID}
MODS: https://webservices.lib.harvard.edu/rest/mods/hollis/{HOLLIS_ID}
DC:   https://webservices.lib.harvard.edu/rest/dc/hollis/{HOLLIS_ID}

PRESTO returns XML only and does not support JSON serialization. ISBN/barcode lookups may not work on all records.

User-Agent header is required

LibraryCloud returns 403 without a User-Agent header. Always include one:

curl -H 'User-Agent: MyApp/1.0' 'https://api.lib.harvard.edu/v2/items.json?title=hamlet'

The Python script includes this automatically.

Rate limit: max 1 request/second, 300 per 5 minutes

Exceeding this triggers a 5-minute lockout. The Python script handles this automatically.

Choosing an Access Method

Typical Workflow: Book Title to Full Bibliography

This is the primary use case — an LLM extracts a book title from a document and needs complete bibliographic data:

from scripts.harvard_api import HarvardLibraryAPI
api = HarvardLibraryAPI()

# 1. Search by title (and optionally author)
results = api.search(title="The Great Gatsby", name="Fitzgerald")

# 2. Get the first match's summary
if results:
    summary = api.summarize(results[0])
    # → title, author, publisher, date, ISBN, subjects, language, physical description

# 3. For deeper data, get MARC via PRESTO
hollis_id = api.get_record_id(results[0])
if hollis_id:
    marc = api.get_presto_record(hollis_id, format="mods")

Key Search Fields

Combine fields freely: ?title=hamlet&name=shakespeare&languageCode=ger&dates.start=1900

Pagination

• limit=N (default 10, max 250)
• start=N for offset-based pagination (up to ~30K results)
• cursor=* then cursor={nextCursor} for large result sets (up to 100K)

Facets

Add facets=field1,field2 to get value counts. Useful fields: name, subject, languageCode, genre, resourceType, repository, dateIssued.

?title=china&facets=languageCode,genre

Python Script

Use scripts/harvard_api.py for programmatic access (zero dependencies):

from scripts.harvard_api import HarvardLibraryAPI
api = HarvardLibraryAPI()

# Keyword search
results = api.search(q="Chinese porcelain Ming dynasty")

# Field search
results = api.search(title="dream of the red chamber", languageCode="chi")

# With facets
results, facets = api.search_with_facets(subject="astronomy", facets=["genre", "dateIssued"])

# Pagination
all_results = api.search_all(title="peanuts", name="schulz", max_results=500)

# PRESTO lookup
marc_xml = api.get_presto_record("011557057", format="marc")

# Summarize a record
for r in results[:5]:
    print(api.summarize(r))

API Endpoints

Related Skills

• wikidata-search: Cross-reference Harvard catalog entries with Wikidata for external identifiers (VIAF, LoC, etc.)
• cbdb-api: Look up authors of Chinese historical texts in CBDB for biographical context

Resources

• references/api_reference.md — Complete field reference with all searchable fields, facets, and query examples
• scripts/harvard_api.py — Full-featured Python client with rate limiting, pagination, and record summarization