All guides

DOI lookup API: paper metadata and citation counts

Resolve a DOI or a citation string to title, authors, journal, year, publisher, citation count and licence links with one call. Pay per lookup.

Reference managers, research agents and literature tools need clean bibliographic facts for a paper. Give a DOI, or a citation text for a best-match search, and the call returns the title, authors, journal, year, publisher, citation count, licence links and the URL.

The answer contains bibliographic facts only; it does not return the paper's text. Failed lookups are not charged.

The calls

Each call returns 402 with the price until a payment is attached; an x402 client pays and retries automatically. Calls that fail are not charged. See Get started and the guide for bots and agents for code.

doi-lookup $0.003 per call

Scholarly metadata by DOI, or a best-match search by citation text: title, authors, journal, year, publisher, citation count, licence links and URL.

curl -i "https://api.ambolt.dev/v1/doi-lookup?doi=10.1038%2Fnature14539"

{
  "doi": "10.1038/nature14539",
  "count": 1,
  "works": [
    {
      "doi": "10.1038/nature14539",
      "title": "Deep learning",
      "type": "journal-article",
      "publisher": "Springer Science and Business Media LLC",
      "container": "Nature",
      "year": 2015,
      "authors": [
        "Yann LeCun",
        "Yoshua Bengio",
        "Geoffrey Hinton"
      ],
      "citedByCount": 77858,
      "referenceCount": 103,
      "licenses": [
        "https://www.springer.com/tdm",
        "https://www.springer.com/tdm"
      ],
      "url": "https://doi.org/10.1038/nature14539"
    }
  ],
  "fetchedAt": "2026-10-02T21:35:41.793Z",
  "source": "Source: Crossref REST API; metadata is available without restriction (CC0 facts)."
}

Questions

Can I search by citation text?

Yes. Pass query instead of doi and use limit for the number of matches.

Does it return the full text?

No. It returns metadata and links, not the article.

How current are citation counts?

They come from the public index at the time of the call and change as new papers are indexed.

Use it from an AI agent

Every call is also an MCP tool: add https://api.ambolt.dev/mcp to your agent's server list.