# crossref-doi

> DOI metadata from Crossref: type, title, container (journal/book), publisher, authors with ORCID and affiliations, dates, volume/issue/pages, ISSN/ISBN, licenses, abstract, subjects, citation counts, funders, and optionally the reference list.

- URL: https://forge-tools.dentreprise.workers.dev/api/crossref-doi (GET or POST)
- Price: 0.002 USDC on Base (2000 atomic USDC)
- MCP tool: crossref_doi
- Docs: https://agent-hub.dentreprise.workers.dev/tools/crossref-doi/

## Parameters

- `doi` (string, required): DOI or doi.org URL
- `references` (string): true to include references

## Unpaid example

```bash
curl -sS -D - "https://forge-tools.dentreprise.workers.dev/api/crossref-doi?doi=10.1038%2Fnature12373"
```

## Example 402 challenge

```json
{
  "x402Version": 2,
  "error": "Payment required",
  "resource": {
    "url": "https://forge-tools.dentreprise.workers.dev/api/crossref-doi",
    "description": "DOI metadata from Crossref: type, title, container (journal/book), publisher, authors with ORCID and affiliations, dates, volume/issue/pages, ISSN/ISBN, licenses, abstract, subjects, citation counts, funders, and optionally the reference list.",
    "mimeType": "application/json"
  },
  "accepts": [
    {
      "scheme": "exact",
      "network": "eip155:8453",
      "amount": "2000",
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "payTo": "0x7B8bf45ac6AcbA6D4CFB626b57D3f5fF3C9C89F7",
      "maxTimeoutSeconds": 120,
      "extra": {
        "name": "USD Coin",
        "version": "2"
      }
    }
  ]
}
```

## Example response

```json
{
  "found": true,
  "title": "Nanometre-scale thermometry in a living cell",
  "container": "Nature"
}
```

## Free demo / sample

This tool accepts `?demo=1` on the wave-1 worker (labelled sample, HTTP 200, not live data). The first 3 successful real calls per IP per UTC day are also free.

```bash
curl -sS "https://forge-tools.dentreprise.workers.dev/api/crossref-doi?doi=10.1038%2Fnature12373&demo=1"
```

```json
{
  "demo": true,
  "demo_label": "DEMO / SAMPLE — not live data. This is a labelled example response and was not charged.",
  "charged": false,
  "tool": "/api/crossref-doi",
  "docs": "https://agent-hub.dentreprise.workers.dev/tools/crossref-doi/",
  "how_to_get_live_data": "Call the same URL without demo=1. The first 3 successful real calls per IP per UTC day are free; after that attach an x402 v2 PAYMENT-SIGNATURE (USDC on Base).",
  "sample": {
    "found": true,
    "title": "Nanometre-scale thermometry in a living cell",
    "container": "Nature"
  }
}
```

## Clients

- JS (x402 v2): `@x402/fetch` + `@x402/evm` (`wrapFetchWithPaymentFromConfig`, `ExactEvmScheme`). The older package `x402-fetch` is deprecated v1.
- Python: PyPI package `x402` (`x402HttpxClient` or `x402_requests`, `register_exact_evm_client`, `EthAccountSigner`).
- MCP: stdio `node src/server.mjs` in [forge-agent-mcp](https://github.com/forge-agent-hub/forge-agent-mcp); hosted Streamable HTTP at https://x402-gateway.forge-x402.workers.dev/mcp (original gateway tools).
- LangChain: wrap those clients with `DynamicStructuredTool` (`@langchain/core`) or `@tool` (`langchain_core`).
- Copy-paste snippets: https://agent-hub.dentreprise.workers.dev/tools/crossref-doi/ and https://agent-hub.dentreprise.workers.dev/quickstart/