# Academic Paper Citations Lookup

> Academic Paper Citations Lookup is a paid API for AI agents from 2s.io, paid per call via x402, $0.006/call, status unknown (last checked 2026-09-15).

Retrieves citing works or bibliography references for a scholarly paper identified by DOI or OpenAlex work ID

## Facts

- Endpoint: GET https://2s.io/api/papers/citations
- Price: $0.006/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/academic-paper-citations-lookup-461f05a3
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8irCB8JOu-85398sVyVDY

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 academic-paper-citations-lookup-461f05a3
```

Example prompt: Can you get me the 10 most-cited papers that cite DOI 10.1038/s41586-020-2649-2? Use the 'citing' view and sort by citations.

## When to prefer this

Use this endpoint when you need to explore the citation graph of a specific academic paper — either who cites it (forward citations) or what it cites (bibliography/references) — and you have a DOI or OpenAlex work ID. Prefer this over general web search for structured, paginated, machine-readable citation data from a comprehensive academic corpus.

## Known failure modes

- Invalid or malformed DOI returns an error or empty result
- Unknown OpenAlex work ID returns 404 or empty list
- Page number beyond available pages returns empty result set
- Limit outside 1–50 range may be rejected or clamped
- Network timeout if OpenAlex upstream is slow
- No citations exist for new or obscure papers — returns empty array

## How this service works

The (most) everything API: 575+ pay-per-call endpoints for AI agents — ground-truth data, a full AI gateway, and agent infrastructure (storage, queues, watchers). USDC via x402, no signup, no API keys, and upto billing: pay actual usage, not the quote.

## Output

A paginated list of academic works (either papers citing the target or papers the target references), each with metadata such as title, authors, publication year, DOI, and citation counts, drawn from OpenAlex's corpus.

## 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",
    "queryParams"
   ],
   "properties": {
    "type": {
     "const": "http"
    },
    "method": {
     "const": "GET"
    },
    "queryParams": {
     "required": [
      "id"
     ],
     "properties": {
      "id": {
       "type": "string",
       "description": "DOI (10.xxxx/…) or OpenAlex work id (W…)."
      },
      "page": {
       "type": "integer",
       "description": "Page number (default 1)."
      },
      "sort": {
       "type": "string",
       "description": "citing view only: 'recent' (default) or 'citations' (most-cited first)."
      },
      "view": {
       "type": "string",
       "description": "'citing' (works that cite it — default) or 'referenced' (its bibliography)."
      },
      "limit": {
       "type": "integer",
       "description": "Results per page (1–50, default 10)."
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/academic-paper-citations-lookup-461f05a3/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 2s.io](https://www.zero.xyz/host/2s.io/llms.txt)