# Evidence402 DOI Citation Verifier

> Evidence402 DOI Citation Verifier is a paid API for AI agents from evidence402.onrender.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-12).

Reads public webpages, extracts structured data, and verifies DOI citations from academic or web content, paid per-call with USDC via x402.

## Facts

- Endpoint: POST https://evidence402.onrender.com/api/v1/verify?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/evidence402-doi-citation-verifier-27229fce
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_EWT2DXkoNMpfCELLKaJJs

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 evidence402-doi-citation-verifier-27229fce -d '<json body>'
```

Example prompt: Can you verify the DOI citations on this webpage — https://example.com/research-article — and tell me which ones are real, valid references and which ones can't be resolved?

## When to prefer this

Choose this endpoint when you need to verify academic DOI citations from web content without managing an API subscription — it's ideal for agents that occasionally need citation validation and prefer pay-per-call USDC billing. Best suited for research integrity checks, bibliography auditing, and extracting structured citation data from public webpages.

## Known failure modes

- Webpage URL is paywalled or requires login — content cannot be fetched
- DOI does not exist or resolves to a 404 — marked as unverifiable
- Rate limiting or network timeout when fetching the target URL
- Invalid DOI format submitted — parsing error returned
- Empty citations array if no DOIs are found in the provided content
- Payment failure via x402 if USDC balance is insufficient

## How this service works

Read public webpages, extract structured data and verify DOI citations. No buyer API key or subscription. Pay per call with x402 USDC on Base.

## Output

Returns a JSON object containing a citations array with verification results for each DOI found or submitted, a service identifier ('Evidence402'), and a requestId for tracking. Each citation entry indicates whether the DOI resolved successfully and may include metadata about the referenced publication.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "data": {
   "citations": []
  },
  "service": "Evidence402",
  "requestId": "example-request"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/evidence402-doi-citation-verifier-27229fce/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from evidence402.onrender.com](https://www.zero.xyz/host/evidence402.onrender.com/llms.txt)