# Unpaywall MCP > Unpaywall MCP Server checks scholarly articles for open access status using a DOI. You enter a Digital Object Identifier (DOI), and it tells you if a journal paper, even one behind a paywall, has a legally available PDF link somewhere else online. It instantly confirms the Open Access status of research papers without needing to navigate multiple university libraries. ## Overview - **Category:** knowledge-management - **Price:** Free - **Tags:** open-access, scholarly-articles, academic-research, doi-lookup, pdf-retrieval, research-database ## Description You run into paywalls all the time when you're doing literature reviews. This server fixes that problem. Your agent connects to the `get_article_oa_status` tool and instantly confirms if any scholarly article is actually open access, regardless of what a publisher tries to charge for it. The whole deal hinges on the Digital Object Identifier (DOI). You feed your client the DOI, and the server does all the heavy lifting. It doesn't just tell you 'yes' or 'no'; it gives you specific data points that let you bypass paywalled content entirely and get straight to the research. When you use this tool, your agent first processes the article’s Open Access status. This check determines if a legally available open-access license exists for the work. It confirms the paper's accessibility before you waste time navigating university library portals or dealing with paywall pop-ups. Knowing the OA status upfront saves huge amounts of time. The tool doesn't stop at just confirming eligibility; it retrieves direct, functional download links for the full text. These are legal PDF downloads sourced from known institutional repositories—not some sketchy file dump. You get a clean link that your agent can use immediately to pull the entire research paper. It pulls those direct links so you don't have to manually search through multiple archives. Furthermore, it gives you metadata on the type of open access available. This means you’ll know if the article falls under green open access (a version uploaded by the author) or gold open access (published directly in an OA journal). That detail is crucial for tracking how research gets disseminated and helps your agent understand the paper's provenance. When you need to process a whole list of papers—say, twenty DOIs from a conference proceedings—you can send multiple identifiers at once. The tool processes all those DOIs efficiently, finding accessible versions across the board so you don’t have to run the checks one by one. It automates the source-finding part of your literature review. This isn't guesswork about whether a paper is open access; it's a technical confirmation using established identifiers and known repository sources. Your agent needs this tool when it's supposed to read an article, but you don't want it stalled out on a payment screen or redirected to a login page. ## Tools ### get_article_oa_status Checks an article's DOI to report its Open Access status and potential download links. ## Prompt Examples **Prompt:** ``` Check the Open Access status for DOI 10.1038/nature12345. ``` **Response:** ``` I've checked the Unpaywall database for DOI 10.1038/nature12345. This article is available via Open Access. You can download the full PDF here: [Link]. ``` **Prompt:** ``` Find a free version of the paper with DOI 10.1126/science.1234567. ``` **Response:** ``` Searching... I found a legal, open-access version of this paper hosted on a university repository. Here is the link to the full text. ``` **Prompt:** ``` Is the article 10.1016/j.cell.2021.01.001 behind a paywall? ``` **Response:** ``` According to Unpaywall, this specific DOI is currently not available as a free Open Access version. It appears to be behind a publisher paywall. ``` ## Capabilities ### Confirm Article Accessibility Checks a provided DOI to determine if the scholarly article has an open-access license. ### Retrieve Direct PDF Links Pulls direct, legal download links for the full-text research paper from known repositories. ### Identify Open Access Type Reports metadata detailing the type of open access available (like green or gold). ### Automate Source Finding Allows your agent to process multiple DOIs and find accessible versions for literature reviews. ## Use Cases ### Reviewing citations for a grant proposal A researcher is writing a literature review and finds several DOIs. Instead of spending an afternoon checking each one on JSTOR or PubMed, they run the DOI list through `get_article_oa_status`. The agent reports back which papers are instantly downloadable as free PDFs, saving hours of manual effort. ### Building a corpus for data science A data analyst needs hundreds of research abstracts and full texts. They feed the DOIs into an agent that uses `get_article_oa_status`. The system filters out paywalled articles, only passing back links to usable open-access PDFs. ### Student accessing required reading A student is assigned readings from a major journal. They input the DOI into their agent and run `get_article_oa_status`. The tool confirms that even if the university library has it locked behind paywalls, a free copy exists on an institutional archive. ### Quickly vetting research claims A team member sends a DOI in a chat about a new finding. Before committing to reading the paid article, you run `get_article_oa_status`. If it fails, you know immediately that the paper is behind a paywall and requires further investigation or payment. ## Benefits - Skip the library portal rabbit hole. Instead of manually searching multiple databases, running `get_article_oa_status` provides an immediate answer about article availability. - Get direct links, not just status flags. When the tool confirms Open Access, it often gives you a usable URL to download the full PDF immediately. - Automate literature reviews efficiently. Your agent runs multiple checks, gathering accessible papers from diverse sources without manual intervention. - Understand the source of access. The server reports if the OA is green (repository) or gold (publisher), giving you context on the file's origin. - Stop paying for articles by accident. This tool validates every DOI against open-access law, confirming if a paper truly requires a subscription. ## How It Works The bottom line is: you give it a DOI, and it gives you the answer—yes or no, and where to download it if yes. 1. First, subscribe to the Unpaywall MCP Server. The API requires you to enter an email address. 2. Second, tell your AI client (Claude, Cursor, etc.) to use the `get_article_oa_status` tool and provide it with a DOI. 3. The server runs the check and returns a structured result containing the Open Access status and any direct PDF links found. ## Frequently Asked Questions **Does Unpaywall (Open Access Papers) MCP Server work for any DOI?** It works for any standard scholarly DOI. The tool is designed to check the global status of academic papers, not just those from one journal or university. **What if a paper isn't open access? Does get_article_oa_status tell me that?** Yes. If the tool checks the DOI and cannot confirm an OA link, it reports that the article appears to be behind a publisher paywall. **Do I need to provide an email address to use get_article_oa_status?** Yes. The server requires you to enter your email address during setup because Unpaywall's API policy mandates it for usage tracking. **Can this tool retrieve the full text if I only have an abstract?** No, the tool needs a DOI. If you only have the abstract or title, first find the corresponding DOI before running `get_article_oa_status`. **What happens if I use `get_article_oa_status` with an invalid or malformed DOI?** The tool returns a specific error message indicating the input was invalid. The system catches these errors, letting you know exactly what went wrong so your agent can correct the data. **Are there any rate limits when calling `get_article_oa_status`?** Usage is subject to Unpaywall's underlying API policy. Vinkius manages quota allocation, and excessive requests will result in a clear rate limit error that your agent can handle. **Does `get_article_oa_status` provide metadata beyond just the PDF link?** Yes, it provides detailed information about the Open Access status. You get data specifying the type of OA (like green or gold) and the source repository. **Which AI clients are compatible with using `get_article_oa_status`?** Since this is an MCP Server on Vinkius, it works with any client that supports the Model Context Protocol. This includes Claude, Cursor, VS Code, and other compatible agents. **How do I check if a specific research paper is available for free?** Use the `get_article_oa_status` tool with the paper's DOI. Your agent will query the Unpaywall database and return the Open Access status along with direct links to the PDF if available. **Does this tool provide legal versions of the papers?** Yes. Unpaywall only indexes legal, author-archived, or publisher-provided Open Access versions of scholarly articles. It does not access pirated content. **What information is required to use this server?** You need the DOI (Digital Object Identifier) of the article and a valid email address to authenticate with the Unpaywall API.