# Research Paper Checks – DOI Bibliographic Metadata

> Research Paper Checks – DOI Bibliographic Metadata is a paid API for AI agents from research-papers.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Fetches clean bibliographic metadata for a research paper by DOI from Crossref, including authors, journal, pages, publisher, license, and a formatted citation string.

## Facts

- Endpoint: GET https://research-papers.x402tookit.com/doi-metadata?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/research-paper-checks-doi-bibliographic-metadata-6dd740db
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Zl-vIAW5X1IzSVeJBa3_Z

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-paper-checks-doi-bibliographic-metadata-6dd740db
```

Example prompt: Can you pull the full bibliographic metadata for the paper with DOI 10.1038/nature12373 — I need the authors, journal, year, publisher, license, and a ready-to-use citation string.

## When to prefer this

Use this endpoint when you need clean, structured bibliographic metadata for a specific paper and have its DOI. It is ideal for citation generation, reference database population, license checking, and author lookup. Prefer it over full paper profile endpoints when you only need core bibliographic fields rather than citation counts or impact metrics.

## Known failure modes

- DOI not found in Crossref — returns null fields or error
- Malformed DOI string — request fails validation
- Crossref API unavailable — degraded flag set or timeout
- Partial metadata — some fields null if Crossref record is incomplete
- DOI exists but has no associated metadata (e.g. very new or obscure record)

## How this service works

Clean bibliographic metadata for a DOI from Crossref: authors, journal, pages, publisher, license, plus a ready citation string.

## Output

Returns a structured object containing the DOI, title, authors (list), journal name, ISSN(s), volume, issue, pages, year, publisher, license, source URL, reference count, a formatted citation string, and metadata freshness timestamp. Fields may be null if not available from Crossref.

## 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"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "doi": {
       "type": [
        "null",
        "string"
       ]
      },
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "issn": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "type": {
       "type": [
        "null",
        "string"
       ]
      },
      "year": {
       "type": [
        "null",
        "number"
       ]
      },
      "issue": {
       "type": [
        "null",
        "string"
       ]
      },
      "pages": {
       "type": [
        "null",
        "string"
       ]
      },
      "title": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "volume": {
       "type": [
        "null",
        "string"
       ]
      },
      "authors": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "journal": {
       "type": [
        "null",
        "string"
       ]
      },
      "license": {
       "type": [
        "null",
        "string"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "citation": {
       "type": [
        "null",
        "string"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/research-paper-checks-doi-bibliographic-metadata-6dd740db/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from research-papers.x402tookit.com](https://www.zero.xyz/host/research-papers.x402tookit.com/llms.txt)