# research.memoryapi.org – Paper Citations & Metadata via Crossref

> research.memoryapi.org – Paper Citations & Metadata via Crossref is a paid API for AI agents from research.memoryapi.org, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Retrieve academic paper citations and metadata using Crossref, supporting both topic-based search and direct DOI lookup

## Facts

- Endpoint: GET https://research.memoryapi.org/x402/research/citations
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/research-memoryapi-org-e839a253
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_rWDE0yXf9TJ5GQ9f5zXHi

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability research-memoryapi-org-e839a253
```

Example prompt: Can you look up the citation metadata for the paper with DOI 10.1038/nature12373, including its authors, journal, publication date, and how many times it's been cited?

## When to prefer this

Use this endpoint when you need authoritative bibliographic metadata or citation counts for academic papers, especially when you have a DOI or a specific research topic in mind and need Crossref-sourced data. Prefer this over OpenAlex search when Crossref coverage is important (e.g., journal articles, DOI-based lookup). Use the OpenAlex endpoint for broader 250M+ work discovery with more filtering options.

## Known failure modes

- DOI not found in Crossref database returns empty or 404-style response
- Malformed DOI input may return no results
- Topic search with very broad or ambiguous terms may return irrelevant results
- Rate limiting or payment failure ($0.005 USDC per call) may block requests
- Crossref API downtime may cause upstream errors

## How this service works

Scientific literature search API with x402 micropayments. Search PubMed, arXiv, and Crossref citations.

## Output

Returns structured citation and bibliographic metadata for matching papers, including title, authors, journal, publication date, DOI, and citation count, sourced from the Crossref database.

## Example request

```json
{
 "doi": "10.1038/nature12373"
}
```

## Response schema (JSON Schema)

```json
{
 "example": {
  "count": 10,
  "query": "machine learning",
  "papers": [
   {
    "doi": "10.1038/s41586-021-03819-2",
    "url": "https://doi.org/10.1038/s41586-021-03819-2",
    "title": "Highly accurate protein structure prediction with AlphaFold",
    "authors": [
     "Jumper J",
     "Evans R"
    ],
    "subjects": [
     "Structural Biology"
    ],
    "publisher": "Nature",
    "citation_count": 22000,
    "published_year": 2021
   }
  ],
  "source": "Crossref",
  "success": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/research-memoryapi-org-e839a253/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from research.memoryapi.org](https://www.zero.xyz/host/research.memoryapi.org/llms.txt)