Physics Papers

{
  "checked_at": "2026-10-15T10:56:51.463Z",
  "papers": [
    {
      "arxiv_id": "astro-ph/9611107",
      "author_count": 3,
      "authors": [
        "Navarro, Julio F.",
        "Frenk, Carlos S.",
        "White, Simon D.M."
      ],
      "citations": 8975,
      "doi": "10.1086/304888",
      "first_date": "1996-11",
      "inspire_url": "https://inspirehep.net/literature/436917",
      "journal": "Astrophys.J.",
      "title": "A Universal density profile from hierarchical clustering",
      "year": 1997
    },
    {
      "arxiv_id": "astro-ph/9508025",
      "author_count": 3,
      "authors": [
        "Navarro, Julio F.",
        "Frenk, Carlos S.",
        "White, Simon D.M."
      ],
      "citations": 7644,
      "doi": "10.1086/177173",
      "first_date": "1995-08",
      "inspire_url": "https://inspirehep.net/literature/406997",
      "journal": "Astrophys.J.",
      "title": "The Structure of cold dark matter halos",
      "year": 1996
    },
    {
      "arxiv_id": "hep-ph/9506380",
      "author_count": 3,
      "authors": [
        "Jungman, Gerard",
        "Kamionkowski, Marc",
        "Griest, Kim"
      ],
      "citations": 5540,
      "doi": "10.1016/0370-1573(95)00058-5",
      "first_date": "1995-06",
      "inspire_url": "https://inspirehep.net/literature/396520",
      "journal": "Phys.Rept.",
      "title": "Supersymmetric dark matter",
      "year": 1996
    }
  ],
  "query": "dark matter halo",
  "sort": "mostcited",
  "source": "INSPIRE-HEP (CERN, DESY, Fermilab, IHEP, IN2P3, SLAC) - metadata CC0",
  "total_matches": 15607
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://saylorinnovations.com/api/physics/papers?limit=5&q=dark+matter+halo'

# 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 - 'https://saylorinnovations.com/api/physics/papers?limit=5&q=dark+matter+halo' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// 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 $0.01 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.01" });
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 $0.01 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fsaylorinnovations.com%2Fapi%2Fphysics%2Fpapers
const res = await pay("https://saylorinnovations.com/api/physics/papers?limit=5&q=dark+matter+halo");
console.log(res.status, await res.text());

# 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 $0.01 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.01"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://saylorinnovations.com/api/physics/papers?limit=5&q=dark+matter+halo")
    print(res.status_code, res.text)