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Open-Access PDF Locator via DOI (Unpaywall + OpenAlex)
x402
Open-Access PDF Locator via DOI (Unpaywall + OpenAlex) is a paid API for AI agents from payai.agentstools.dev, paid per call via x402, $0.008/call, status unknown (last checked 2026-09-14).
Given a DOI, checks whether a free open-access PDF exists and returns the best PDF link along with its license, version, and host type.
Price / call$0.008
Success—
StatusUnknown
How this service works
Locate a free open-access PDF for a DOI. Returns whether an open-access copy exists and the best PDF link with its license, version and host type, from Unpaywall and OpenAlex. A cheap, focused open-access locator.
Output
Returns whether an open-access copy exists (boolean), the best available PDF URL, the license (e.g. CC-BY), the version (e.g. publishedVersion, acceptedVersion), and the host type (e.g. repository, publisher). Sourced from Unpaywall and OpenAlex.
Example use cases
Research literature collection for systematic review
“I'm compiling sources for a systematic review on climate adaptation strategies. Can you go through these DOIs and find me free PDFs for each one, including what license they're under and whether they're published or accepted versions?”
Verify journal article accessibility before citing
“Before I cite this paper in my grant proposal, can you check if there's a free open-access version available with DOI 10.1016/j.envsoft.2022.105432? I need to know if it's actually freely available and what the terms are.”
Build a legal open-access paper repository
“We're creating an internal knowledge base for our team. Can you batch-check these 20 DOIs to see which ones have free open-access PDFs, and for each one, tell me the best download link, the license type, and whether it's the final published version?”
Technical details
Endpoint
GEThttps://payai.agentstools.dev/scholar/oaWhen to prefer
Use this endpoint when you have a specific DOI and need to quickly determine whether a free legal PDF exists, and where to get it. It is cheaper and more focused than a full paper metadata resolver. Prefer it over general web search when you want structured, license-aware open-access data from authoritative sources (Unpaywall + OpenAlex) rather than scraping or guessing.
Side effects
- DOI not found in Unpaywall or OpenAlex — returns no open-access record
- Invalid or malformed DOI — returns an error or empty result
- Paper exists but has no open-access copy — returns is_oa: false with no PDF link
- Upstream Unpaywall/OpenAlex service unavailable — timeout or 5xx error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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