# Academic Paper Metadata Resolver (payai.agentstools.dev)

> Academic Paper Metadata Resolver (payai.agentstools.dev) is a paid API for AI agents from payai.agentstools.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-11).

Resolves a research paper by any identifier (DOI, arXiv, PMID, PMCID, OpenAlex ID, or title) and returns fused canonical metadata from OpenAlex, Crossref, Unpaywall, and Semantic Scholar in a single JSON response.

## Facts

- Endpoint: GET https://payai.agentstools.dev/scholar/paper?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/academic-paper-metadata-resolver-payai-agentstools-dev-6bd8c6c4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yTRmfKH0Tvh6hDwpEK7Zr

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-metadata-resolver-payai-agentstools-dev-6bd8c6c4
```

Example prompt: Can you pull the full metadata for the paper with DOI 10.1038/s41586-021-03819-2 — I need the authors with their ORCIDs and affiliations, citation count, venue, and an open-access PDF link if one exists.

## When to prefer this

Use this endpoint when you need a single authoritative, source-fused metadata record for a known academic paper and want to avoid making separate API calls to OpenAlex, Crossref, Unpaywall, and Semantic Scholar. Ideal when you need author ORCID/affiliation data, citation counts, open-access PDF links, and cross-database ID mapping all in one call. Prefer over the sibling open-access-only endpoint when you need full bibliographic metadata beyond just the PDF link.

## Known failure modes

- Paper not found by any source — returns empty or 404-like response if identifier is unrecognized
- Title search ambiguity — fuzzy title matching may return wrong paper if title is common or partial
- Partial metadata — some fields (e.g. ORCID, PDF link) may be null if upstream sources lack coverage
- Invalid identifier format — malformed DOI or arXiv ID results in a bad request error
- No open-access PDF — Unpaywall may confirm paper exists but return null for PDF URL

## How this service works

Resolve one research paper and fuse its metadata across OpenAlex, Crossref, Unpaywall and Semantic Scholar into a single cited JSON. Give a doi, arxiv, pmid, pmcid, openalex_id or title and get canonical metadata, authors with ORCID and affiliations, venue, citation counts, an open-access PDF link and a full id crosswalk.

## Output

A single JSON object containing canonical paper metadata fused from OpenAlex, Crossref, Unpaywall, and Semantic Scholar: title, authors with ORCID and institutional affiliations, publication venue, year, citation count, open-access PDF URL, and a full identifier crosswalk mapping DOI, arXiv ID, PMID, PMCID, OpenAlex ID, and Semantic Scholar ID.

## 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",
     "required": [],
     "properties": {
      "id": {
       "type": "string",
       "description": "Any single identifier; its type is auto-detected"
      },
      "doi": {
       "type": "string",
       "description": "DOI, with or without a doi.org prefix"
      },
      "pmid": {
       "type": "string",
       "description": "PubMed id (digits)"
      },
      "arxiv": {
       "type": "string",
       "description": "arXiv id such as 2401.01234"
      },
      "pmcid": {
       "type": "string",
       "description": "PubMed Central id such as PMC1234567"
      },
      "title": {
       "type": "string",
       "description": "Paper title to resolve by search"
      },
      "openalex_id": {
       "type": "string",
       "description": "OpenAlex work id such as W2741809807"
      }
     }
    }
   },
   "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/academic-paper-metadata-resolver-payai-agentstools-dev-6bd8c6c4/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from payai.agentstools.dev](https://www.zero.xyz/host/payai.agentstools.dev/llms.txt)