# CrossRef DOI Scholarly Metadata Lookup

> CrossRef DOI Scholarly Metadata Lookup is a paid API for AI agents from api.x402node.dev, paid per call via x402, $0.008/call, status unknown (last checked 2026-09-15).

Retrieves scholarly metadata for a given DOI via CrossRef, including title, authors, journal, publication date, abstract, citation count, references, license, and URL.

## Facts

- Endpoint: GET https://api.x402node.dev/citation/doi
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/api-x402node-dev-828d6d9b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_uY3VIB9m1IXbrk5pz1QHL

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 api-x402node-dev-828d6d9b
```

Example prompt: Can you pull up the full metadata for the paper with DOI 10.1038/nature12373 — I need the title, authors, journal, abstract, citation count, and any references listed?

## When to prefer this

Use this endpoint when you need authoritative bibliographic metadata for a specific DOI, especially for literature review, citation graph traversal, or academic research workflows. Prefer over generic web search when you have a known DOI and need structured citation data from CrossRef's curated index.

## Known failure modes

- DOI not found in CrossRef index — returns 404 or empty result
- Malformed DOI string — returns validation error
- CrossRef upstream timeout — returns 5xx or timeout error
- Paper exists but has incomplete metadata — some fields may be null or absent
- Rate limit or payment failure — returns 402 or 429

## How this service works

Look up scholarly metadata for any DOI via CrossRef. Returns title, authors, journal, publication date, abstract, citation count, references, license, URL. Use ?doi=10.1038/nature12373. Built for AI research agents doing literature review and citation graph traversal. Accepts payment on Base or Solana — either network works.

## Output

Returns structured scholarly metadata including paper title, author list, journal name, publication date, abstract text, citation count, reference list, license information, and canonical URL for the resolved DOI.

## Example request

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

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "doi"
     ],
     "properties": {
      "doi": {
       "type": "string",
       "description": "DOI string (required)"
      }
     }
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/api-x402node-dev-828d6d9b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.x402node.dev](https://www.zero.xyz/host/api.x402node.dev/llms.txt)