# GET /papers/get: $0.002 per call

One academic paper by DOI: title, authors, year, journal, publisher, type, licence, citation count, abstract, PubMed/PMC ids and a free full-text link when open access. Pass ?doi=10.1038/nature12373 (a doi.org link works too). From Crossref and Europe PMC.

- **Price:** $0.002 in USDC, the same on Base, Solana, Polygon, Arbitrum. Failed calls are never charged.
- **Free trial:** yes, 20 free calls a day from Claude, Cursor or any MCP client ([set-up](/mcp/setup)).
- **Answers cached for:** 1 day(s)
- **Data sources:** Crossref REST API (free); Europe PMC REST API (free)
- **Lane:** Academic papers ([OpenAPI](/openapi/scholar.json))
- **Live health:** [status page](/status)

## Free sample

See an answer for the demo input first, free (no payment, 10 a minute): [https://aayatai.com/sample/papers-get](/sample/papers-get). It is a stored real answer when we have one, otherwise an example marked `"kind": "illustrative"`.

```bash
curl "https://aayatai.com/sample/papers-get"
```

## 1. See the price (free)

Call it without paying: you get `402 Payment Required` and a `PAYMENT-REQUIRED` header with the exact price and where to pay.

```bash
curl -i "https://aayatai.com/papers/get?doi=10.1038%2Fnature12373"
```

## 2. Pay and call (TypeScript)

```bash
npm install @x402/fetch @x402/evm viem
```

```ts
import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";

// A wallet used only by your agent, holding a little USDC on Base.
const account = privateKeyToAccount(process.env.WALLET_PRIVATE_KEY as `0x${string}`);
const pay = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(account) }],
});

const res = await pay("https://aayatai.com/papers/get?doi=10.1038%2Fnature12373");
console.log(await res.json());
```

## 3. Or as an MCP tool

```ts
// MCP server: https://aayatai.com/mcp (Streamable HTTP). With the x402 MCP client (see /start):
const result = await client.callTool("papers-get", {"doi":"10.1038/nature12373"});
```

## Inputs

- `doi` **(required)** (string): The DOI, e.g. 10.1038/nature12373 or https://doi.org/10.1038/nature12373.

Bad inputs are rejected with HTTP 400 before any payment is asked for.

## Example answer

Example only: the shape of an answer, with placeholder addresses and made-up figures. It is not data about any real token or wallet; call the service (or its free sample) for real results.

```json
{
  "title": "Nanometre-scale thermometry in a living cell.",
  "authors": "Kucsko G, Maurer PC, Yao NY, Kubo M, Noh HJ, Lo PK, Park H, Lukin MD.",
  "year": 2013,
  "venue": "Nature",
  "type": "journal-article",
  "doi": "10.1038/nature12373",
  "url": "https://doi.org/10.1038/nature12373",
  "openAccessUrl": "https://europepmc.org/articles/PMC4221854?pdf=render",
  "citations": 1832,
  "abstract": "Sensitive probing of temperature variations on nanometre scales is an outstanding challenge…",
  "ids": {
    "pmid": "23903748",
    "pmcid": "PMC4221854"
  },
  "sources": [
    "Europe PMC",
    "Crossref"
  ],
  "publisher": "Springer Science and Business Media LLC",
  "license": null
}
```

## Related

- [GET /papers/search](/services/papers-search) ($0.003): Search academic papers across Europe PMC (PubMed, PMC, preprints) and Crossref (all disciplines), merged by DOI: title, authors, year, journal, DOI, abstract, c

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