# 2s.io DOI Bibliographic Metadata Lookup

> 2s.io DOI Bibliographic Metadata Lookup is a paid API for AI agents from 2s.io, paid per call via x402, $0.0012/call, status unknown (last checked 2026-09-14).

Resolves a DOI to full authoritative bibliographic metadata via Crossref, returning title, authors, journal, publisher, dates, abstract, citations, and more.

## Facts

- Endpoint: GET https://2s.io/api/paper/doi-lookup
- Price: $0.0012/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/2s-io-a6cbf371
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-GuNGEF4x5gPR-1_mR34W

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 2s-io-a6cbf371
```

Example prompt: Can you look up the full bibliographic details for this DOI — 10.1038/nature12373 — including the title, authors with their affiliations, journal name, publisher, publication date, and abstract?

## When to prefer this

Use this endpoint when you have a known DOI and need authoritative, structured bibliographic metadata including authors, affiliations, ORCIDs, abstract, citation counts, and licensing. It covers ~160M works via Crossref — the canonical registry for academic DOIs. Prefer this over general web search when you need machine-readable citation data, or over PubMed when the paper is outside the biomedical domain.

## Known failure modes

- DOI not found in Crossref index (404) — DOI may be valid but not registered with Crossref
- Malformed DOI input — bare DOI or full URL must be syntactically valid
- Crossref upstream unavailable — transient 5xx error
- Payment failure — x402 micropayment not processed correctly
- DOI exists but metadata is incomplete — some older records may lack abstract or author ORCID

## How this service works

Resolve a DOI to authoritative bibliographic metadata via Crossref. Accepts bare DOI (10.1038/nature12373) or full DOI URL (https://doi.org/10.1038/nature12373). Returns work type, title, container (journal/conference), publisher, issued/published dates, abstract, authors (with ORCID + affiliations), page range, volume/issue, ISBN + ISSN lists, canonical URL, reference + citation counts, license blocks, and subject classifications. ~160M works in Crossref. Best authoritative DOI → bibliographic resolver. Metadata is CC0.

## Output

A structured record containing the work type, title, container name (journal or conference), publisher, issued and published dates, abstract, author list with ORCID IDs and institutional affiliations, page range, volume and issue numbers, ISBN and ISSN lists, canonical DOI URL, reference count, citation count, license blocks, and subject classifications — sourced from Crossref's index of ~160 million works under CC0 license.

## Example request

```json
{
 "input": {
  "type": "http",
  "method": "GET",
  "queryParams": {
   "doi": "10.1371/journal.pone.0000000"
  }
 }
}
```

## 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": [
      "doi"
     ],
     "properties": {
      "doi": {
       "type": "string",
       "description": "DOI (bare or https://doi.org/...)."
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/2s-io-a6cbf371/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)