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Northline DOI Open Access Lookup
x402
Northline DOI Open Access Lookup is a paid API for AI agents from 206-81-14-131.sslip.io, paid per call via x402, $0.008/call, status unknown (last checked 2026-10-02).
Looks up open-access availability and metadata for a scholarly article given its DOI
Price / call$0.008
Success—
StatusUnknown
How this service works
Pay-per-call APIs, paid downloads and work-on-request for agents. Payment: x402 (USDC on Base, eip155:8453), no accounts or API keys. Catalog: https://206-81-14-131.sslip.io/?format=json. Agent guide: https://206-81-14-131.sslip.io/llms.txt
Output
Returns open-access status of the article (e.g. gold, green, hybrid, or closed), a direct URL to the freely available PDF or full text if one exists, and bibliographic metadata such as title, authors, journal name, publication year, and license type.
Example use cases
Verify free access before paywalled download
“I found this paper I want to read — DOI is 10.1126/science.abm4573 — can you check if it's available for free anywhere legally before I pay for it?”
Research pipeline open-access screening
“For the DOI 10.1016/j.cell.2022.09.028, look up whether it's open access and what license it's under so I know if I can reproduce figures from it.”
Retrieve citation metadata for a bibliography
“I need the full metadata — title, authors, journal, year — for the article with DOI 10.1101/2023.01.10.523456, and tell me if there's an open access version available.”
Technical details
Endpoint
GEThttps://206-81-14-131.sslip.io/svc/doi-open-access/lookup?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to programmatically check open-access availability for a known DOI without setting up accounts or API keys. Ideal for research agents that need to verify free-access paths before fetching full text, or for enriching citation lists with access URLs. Prefer this over direct publisher APIs when you want a pay-per-call model with no subscription overhead.
Side effects
- DOI not found in open-access index — returns empty or not-found response
- Malformed or non-existent DOI provided — returns error
- Article exists but has no open-access version — returns closed status with no PDF link
- Upstream data source (e.g. Unpaywall) unavailable — may return timeout or 5xx
- Rate limiting or payment failure via x402 protocol — returns 402 Payment Required
Tags
x402
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