ToolVet
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Research Crossref Doi Metadata

by API Acre in Other

x402 APIPassing, checked 2 h ago

Resolve one DOI into normalized open Crossref bibliographic, author, container, citation-count, license, identifier, and correction or retraction-link metadata without abstracts or full text.

POST
https://apiacre.com/v1/research/crossref-doi-metadata
Price
$0.003
per call in USDC
Uptime
96.7%
last 30 days
Response time
221 ms
351 ms slowest 5%
Last check
Passed
2 h ago, next any minute now

Run a free test callHow to call it

Reliability

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Status and outage history · Atom feed · Watch with other listings

How to call it

POST https://apiacre.com/v1/research/crossref-doi-metadata

Each call costs $0.003 in USDC on Base, paid with the request over x402.

Run a free test callOne unpaid request, the way an agent sends it. You see the payment challenge it gets back. Nothing is charged.

Example request

From the listing.

POST https://apiacre.com/v1/research/crossref-doi-metadata
content-type: application/json

{
  "doi": "10.1038/s41586-021-03819-2"
}

Parameters

ParameterTypeRequiredDescription
doistringYes

Example response

The provider's example. We can't check it without paying.

Example response, 35 lines
{
  "data": {
    "documentation": "https://www.crossref.org/documentation/retrieve-metadata/rest-api/",
    "doi": "10.1038/s41586-021-03819-2",
    "limitations": [
      "Demonstration metadata only; paid calls return the current DOI record.",
      "Abstracts and full text are deliberately excluded."
    ],
    "metadataLicense": {
      "abstractsReturned": false,
      "name": "Open bibliographic metadata / Crossref-generated data CC0",
      "url": "https://www.crossref.org/documentation/retrieve-metadata/"
    },
    "retrievedAt": "2026-08-20T12:00:00+00:00",
    "source": "https://api.crossref.org/works/10.1038%2Fs41586-021-03819-2",
    "status": "matched",
    "work": {
      "authors": [],
      "doi": "10.1038/s41586-021-03819-2",
      "publishedDate": "2021-08-25",
      "title": "Example normalized DOI record",
      "type": "journal-article"
    }
  },
  "meta": {
    "cached": false,
    "duration_ms": 42,
    "next_actions": [],
    "sources": [],
    "warnings": []
  },
  "request_id": "018f1f54-7f38-7ba2-8dc3-5f90272d9f1a",
  "service": "research.crossref-doi-metadata",
  "version": "1"
}

Call it from code

The curl command shows the payment challenge. The JavaScript and Python versions pay and call, and never pay more than $0.003.

curl: see the payment challenge
# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://apiacre.com/v1/research/crossref-doi-metadata' \
  -H 'content-type: application/json' \
  --data-raw '{"doi":"10.1038/s41586-021-03819-2"}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://apiacre.com/v1/research/crossref-doi-metadata' \
  -H 'content-type: application/json' \
  --data-raw '{"doi":"10.1038/s41586-021-03819-2"}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode
JavaScript: pay and call
// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.003 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.003" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.003 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fapiacre.com%2Fv1%2Fresearch%2Fcrossref-doi-metadata&method=POST
const res = await pay("https://apiacre.com/v1/research/crossref-doi-metadata", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "doi": "10.1038/s41586-021-03819-2"
  }),
});
console.log(res.status, await res.text());
Python: pay and call
# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.003 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.003"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://apiacre.com/v1/research/crossref-doi-metadata",
        json={
            "doi": "10.1038/s41586-021-03819-2",
        },
    )
    print(res.status_code, res.text)

Security scan

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