# Paper Citation Lookup & Reference Graph

> Paper Citation Lookup & Reference Graph is a paid API for AI agents from api.kadec0.xyz, paid per call via x402, $0.03/call, status unknown (last checked 2026-09-14).

Given a DOI, arXiv ID, OpenAlex ID, or PMID, returns a paper's full metadata, reference list (works it cites), citing-works list (recent papers that cite it), and citation count.

## Facts

- Endpoint: GET https://api.kadec0.xyz/v1/paper-details
- Price: $0.03/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/paper-citation-lookup-reference-graph-4514a060
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XO6Gpif3QeTg7CE3xLZou

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 paper-citation-lookup-reference-graph-4514a060
```

Example prompt: Can you pull up the full reference list and the papers that cite arXiv:2310.06825, showing up to 50 references and 30 citing works?

## When to prefer this

Use this endpoint when you need structured citation data — references or citing works — for a specific paper identified by DOI, arXiv ID, OpenAlex ID, or PMID. Prefer it over general web search when you need machine-readable bibliography data, citation counts, or want to traverse a citation graph programmatically. It requires no API key and costs a flat $0.03 per call via x402.

## Known failure modes

- Unknown or malformed ID returns 404 or empty result
- Paper exists but has no indexed references (e.g. very new or obscure paper)
- PMID or OpenAlex ID not resolvable to a known record
- ref_limit or cite_limit out of 0-100 range returns validation error
- Rate limiting or upstream OpenAlex/Semantic Scholar outage causes 5xx response

## How this service works

Citation lookup and reference list for a paper. Given a DOI, arXiv id, OpenAlex id, or PMID, returns its references (the works it cites) and its cited-by list (recent works that cite it), plus full metadata and citation count — for bibliography building and citation lookup. Keyless via OpenAlex and Semantic Scholar.

## Output

Returns the paper's full metadata (title, authors, abstract, publication date, venue), a list of works it cites (up to ref_limit), a list of recent works that cite it (up to cite_limit), and its total citation count — all drawn from OpenAlex and Semantic Scholar without requiring an API key.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "anyOf": [
      {
       "required": [
        "id"
       ]
      },
      {
       "required": [
        "doi"
       ]
      }
     ],
     "required": [],
     "properties": {
      "id": {
       "type": "string",
       "description": "arXiv id, DOI, OpenAlex id, or PMID"
      },
      "doi": {
       "type": "string",
       "description": "alias for id (DOI form)"
      },
      "ref_limit": {
       "type": "string",
       "default": "25",
       "description": "max references (0-100)"
      },
      "cite_limit": {
       "type": "string",
       "default": "25",
       "description": "max citing works (0-100)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/paper-citation-lookup-reference-graph-4514a060/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.kadec0.xyz](https://www.zero.xyz/host/api.kadec0.xyz/llms.txt)