# Cited Brief DOI Checker

> Cited Brief DOI Checker is a paid API for AI agents from cited-brief.cited-brief.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-18).

Validates DOIs, arXiv IDs, and doi.org links against Crossref to confirm existence, check for retractions, and verify cited titles match the real publication metadata.

## Facts

- Endpoint: POST https://cited-brief.cited-brief.workers.dev/check-doi?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-18
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/cited-brief-doi-checker-3fa83b80
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_tDsAUQgUBvI2AtVOjaDP1

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 cited-brief-doi-checker-3fa83b80 -d '<json body>'
```

Example prompt: Can you check these three DOIs from my paper's reference list — 10.1038/nature12373, 10.1126/science.1234567, and 10.1101/2021.01.01.425001 — and tell me if they're real, whether any have been retracted, and whether the titles I listed match the actual publications?

## When to prefer this

Use this endpoint when you need to validate academic references at scale, particularly to catch hallucinated citations from LLMs, verify title accuracy, or screen for retracted papers. Prefer it over manual Crossref queries when checking batches of up to 10 DOIs at once with title comparison built in. Ideal for agents performing literature review quality assurance, manuscript preparation assistance, or fact-checking of AI-generated academic content.

## Known failure modes

- DOI not found in Crossref — returned with found:false
- arXiv ID does not resolve to a valid paper
- Title mismatch detected — title_ok:false and title_match score below threshold
- Input array exceeds 10 items — rejected by schema validation
- Malformed DOI or URL that cannot be parsed
- Crossref API unavailable or rate-limited — upstream error returned
- Payment not completed via x402 — request blocked before processing

## How this service works

Pay-per-call web research tools for AI agents, paid in USDC over x402.

## Output

A JSON object containing a summary count of found, not_found, and retracted papers, plus per-DOI details including resolved URL, publication type, year, venue, publisher, author list, citation count, retraction status, title match score (0–1), and any notices about the paper.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "ids": {
   "type": "array",
   "items": {
    "type": "string"
   },
   "maxItems": 10,
   "minItems": 1,
   "description": "DOIs (10.xxxx/...), doi.org links or arXiv ids"
  },
  "titles": {
   "type": "array",
   "items": {
    "type": "string"
   },
   "maxItems": 10,
   "description": "Titles you cited, in the same order as ids, to compare with the real ones"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "found": 2,
  "checked": 2,
  "results": [
   {
    "doi": "10.1038/nature12373",
    "url": "https://doi.org/10.1038/nature12373",
    "kind": "doi",
    "type": "journal-article",
    "year": 2013,
    "found": true,
    "input": "10.1038/nature12373",
    "title": "Nanometre-scale thermometry in a living cell",
    "venue": "Nature",
    "source": "crossref",
    "authors": [
     "G. Kucsko",
     "P. C. Maurer"
    ],
    "notices": [],
    "cited_by": 1200,
    "title_ok": true,
    "published": "2013-08",
    "publisher": "Springer Science and Business Media LLC",
    "retracted": false,
    "title_match": 1,
    "author_count": 9
   }
  ],
  "not_found": 0,
  "retracted": 0
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/cited-brief-doi-checker-3fa83b80/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from cited-brief.cited-brief.workers.dev](https://www.zero.xyz/host/cited-brief.cited-brief.workers.dev/llms.txt)