# OpenAlex API - LLM Reference

OpenAlex is an open catalog of the global research system with 270M+ works, 90M+ authors, and 100K+ sources.

## Quick Start

Base URL: https://api.openalex.org
Auth: api_key parameter (free at openalex.org/settings/api)
Rate limit: $1/day free usage with key, $0.01/day without

## Entity Endpoints

GET /works - Scholarly documents (articles, books, datasets, theses)
GET /works/{id} - Single work by OpenAlex ID (W2741809807) or DOI
GET /authors - Researcher profiles
GET /authors/{id} - Single author by ID (A5023888391) or ORCID
GET /sources - Journals, repositories, conferences
GET /institutions - Universities, organizations
GET /topics - Research topic classifications
GET /keywords - Keywords from works
GET /publishers - Publishing organizations
GET /funders - Funding agencies
GET /autocomplete/{entity} - Fast typeahead search

## CRITICAL: Always Resolve Names to IDs

WRONG: /works?filter=authorships.author.display_name:Einstein
RIGHT:
  1. /authors?search=Einstein → get id "A5012345678"
  2. /works?filter=authorships.author.id:A5012345678

Names are ambiguous. IDs are not.

## Query Parameters

api_key=YOUR_KEY - Required for rate limits
filter= - Filter results (field:value)
search= - Full-text search
sort= - Sort field (e.g., cited_by_count:desc)
per_page= - Results per page (max 100)
page= - Page number
cursor= - Deep pagination (use cursor=* to start)
sample= - Random sample (max 10000)
select= - Limit fields returned
group_by= - Aggregate by field

## Filter Syntax

Single: ?filter=publication_year:2024
AND: ?filter=publication_year:2024,is_oa:true
OR: ?filter=type:article|book|dataset (max 100 values)
NOT: ?filter=type:!paratext
Range: ?filter=publication_year:2020-2024
Comparison: ?filter=cited_by_count:>100

## Common Work Filters

authorships.author.id - Filter by author
authorships.institutions.id - Filter by institution
primary_location.source.id - Filter by journal/source
topics.id - Filter by topic
publication_year - Year (integer)
cited_by_count - Citation count
is_oa - Open access (true/false)
type - article, book, dataset, etc.
has_fulltext - Has searchable text

## Example Queries

# Get highly cited 2024 articles
/works?filter=publication_year:2024,type:article,cited_by_count:>50&sort=cited_by_count:desc&per_page=100

# Get open access works from an institution
/works?filter=authorships.institutions.id:I27837315,is_oa:true&per_page=100

# Bulk DOI lookup (up to 50)
/works?filter=doi:10.1234/a|10.1234/b|10.1234/c&per_page=50

# Random sample with seed
/works?sample=100&seed=42

# Count works by topic
/works?filter=publication_year:2024&group_by=topics.id

## Pricing

Singleton (/works/W123): Free
List (/works?filter=...): $0.0001
Search (?search=): $0.001
Content download (PDF): $0.01

## Limits

OR values per filter: 100
per_page max: 100
sample max: 10,000
Basic paging: 10,000 results (use cursor for more)

## Deprecated - Do Not Use

- /concepts → Use /topics
- /text endpoint → Removed
- host_venue field → Use primary_location
- grants field → Use funders and awards

## External ID Formats

DOI: /works/https://doi.org/10.1234/example or /works/doi:10.1234/example
PMID: /works/pmid:29456894
ORCID: /authors/https://orcid.org/0000-0001-6187-6610
ROR: /institutions/https://ror.org/0161xgx34
ISSN: /sources/issn:2167-8359

## Response Format

{
  "meta": {
    "count": 286750097,
    "page": 1,
    "per_page": 25
  },
  "results": [...],
  "group_by": []
}

## Links

Docs: https://developers.openalex.org
API Key: https://openalex.org/settings/api
OpenAPI Spec: https://developers.openalex.org/api-reference/openapi.json