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Open-access linksUnpaywall REST API v2

Unpaywall

Unpaywall is an open database of legal open-access copies of scholarly articles released under CC0. In ScholarMuse it works inside get_paper: when the paper's own record has a DOI but no open-access link, the tool asks Unpaywall for the best open copy and adds the link to the result.

ScholarMuse tools: get_paper. Each successful call uses credits.

Use in my agent

Ask your agent

Get the details of Kahneman and Tversky's 1979 'Prospect Theory' paper and tell me if a legal open copy exists.
I can't access the paper with this DOI through my library. Is there an open-access version, and which version is it?
For each DOI in my reading list, look up the paper and give me an open-access link where one exists.

What your agent gets back

Every record carries id, source, title, url, license, attribution and retrievedAt. The fields below are the data that comes from Unpaywall.

get_paper

Added only when the paper has a DOI, the first source gave no open-access link, and Unpaywall knows an open copy. Only these four fields come from Unpaywall.

openAccess
Set to true when Unpaywall finds an open copy
openAccessUrl
PDF link of the best open copy, or its page
openAccessVersion
publishedVersion, acceptedVersion or submittedVersion
openAccessSource
Set to unpaywall when the link came from it

What it covers

  • Open-access locations for works with a DOI, as known to Unpaywall.
  • The best location Unpaywall reports is used, whether on the publisher site or in a repository.

Limits

  • There is no separate Unpaywall tool. It runs only inside get_paper, one DOI per call.
  • It is skipped when the first source already returned an open-access link, and it needs a DOI.
  • Only the link and version of the best copy are passed on. OA status colour, host type, licence and other locations are not returned.
  • If the Unpaywall request fails, get_paper returns the paper without a link and does not report the failure.

How ScholarMuse reaches Unpaywall

The connector calls api.unpaywall.org/v2/<DOI> directly. Unpaywall has no API key; the request carries a contact email, as its API requires.

Responses are cached for up to 7 days, so a copy that became open this week can take that long to appear.

API key: the upstream API can be called without one, so you do not add one.

Licence and attribution

Licence: CC0-1.0

Open-access locations from Unpaywall (unpaywall.org), CC0.

The get_paper record keeps the licence and attribution of the source that supplied the paper. Unpaywall is named in its openAccessSource field. When you cite the data in a paper, follow Unpaywall's own citation guidance.

Capabilities that use Unpaywall

Search papers

Search papers

All disciplines · OpenAlex, PubMed / Europe PMC, arXiv +5

Related sources

OpenAlexPubMed / Europe PMCarXivbioRxiv / medRxivDBLPINSPIRE-HEPERIC

FAQ

ScholarMuse is not an official Unpaywall product. It is one MCP server for academic data, and its get_paper tool queries Unpaywall. An agent connected to ScholarMuse can use Unpaywall without a separate server.

No. The Unpaywall API can be called without a key, and ScholarMuse does not ask you for one. You sign in to ScholarMuse once and your agent calls the tool.

The connector calls api.unpaywall.org/v2/<DOI> directly. Unpaywall has no API key; the request carries a contact email, as its API requires. Responses are cached for up to 7 days, so a copy that became open this week can take that long to appear.

CC0-1.0. Attribution: Open-access locations from Unpaywall (unpaywall.org), CC0. The get_paper record keeps the licence and attribution of the source that supplied the paper. Unpaywall is named in its openAccessSource field.

Yes. Each successful call to get_paper uses credits, and a call that fails is not charged. Current price: Search papers, 1 credit / call.