checkOpenAccess

Resolves an identifier to a DOI, then looks up its open-access status via Unpaywall. Returns the best legal full-text location (preferring publisher copies, then repository copies), the licence, and the version (preprint, accepted, or published).

When to use

• A user asks "is there a free copy?" or "where can I read this without a paywall?"
• An agent is preparing a reading list and wants to surface freely-readable links.
• A library or syllabus tool wants to filter recommendations by accessibility.

Inputs

• id (string, required) — one identifier per call: DOI, PMID, PMCID, arXiv ID, ISBN, or ADS bibcode. Pass it verbatim. Items with no DOI return a "no DOI" result.

Outputs