FreeCitation for AI Assistants: MCP Citation Server

Server address (Streamable HTTP, no key needed)

https://freecitation.org/mcp

Two tools

cite_source

Takes a DOI, an ISBN, a web address or UK legislation and a style, and returns the reference entry in APA, MLA, Chicago, Harvard, IEEE, Vancouver, AMA, Turabian, Oxford or OSCOLA, built from the real record.

check_references

Takes a reference list in any style and reports, entry by entry, which are verified, which have details that differ from the record, and which have a DOI nobody registered or no record at all.

Both tools only read public records. They never write anything, and they never return a citation they could not find: when Crossref, Open Library and the page itself have nothing, the answer says so. The methodology page explains where each record comes from.

Set it up

Claude

In Claude, open Settings, then Connectors, and choose Add custom connector. Name it FreeCitation and paste the address below. No key or sign in is needed.

Connector address

https://freecitation.org/mcp

Claude Code

Run this once in a terminal:

Terminal

claude mcp add --transport http freecitation https://freecitation.org/mcp

ChatGPT

ChatGPT adds custom MCP servers in developer mode: Settings, Apps and Connectors, Advanced settings. Create a connector with the address below and no authentication. Developer mode is not available on every plan.

Server address

https://freecitation.org/mcp

Cursor

Add this to ~/.cursor/mcp.json, or to .cursor/mcp.json in a project:

mcp.json

{
  "mcpServers": {
    "freecitation": { "url": "https://freecitation.org/mcp" }
  }
}

VS Code

Add this to .vscode/mcp.json in your workspace, then start the server from the file:

.vscode/mcp.json

{
  "servers": {
    "freecitation": { "type": "http", "url": "https://freecitation.org/mcp" }
  }
}

Gemini CLI

Add this to ~/.gemini/settings.json:

settings.json

{
  "mcpServers": {
    "freecitation": { "httpUrl": "https://freecitation.org/mcp" }
  }
}

Things to ask

“Cite 10.1038/nature14539 in Chicago.”
“Give me the OSCOLA citation for the Human Rights Act 1998, section 6.”
“Check the references at the end of my essay before I submit it.”
“You gave me five sources earlier. Check them with FreeCitation.”

The last one matters most. A chatbot that answered from memory can give you a reference with a real journal, real looking authors and a DOI that leads nowhere. Our article on fake AI citations shows how often that happens; the reference checker does the same check in your browser.

Limits

No key and no account are needed. Each connection can make 120 citations and 30 reference checks an hour, with up to 5 references in each check. Calls from a shared platform count together, so a busy hour can reach the limit sooner; the answer then says when to try again. For whole reference lists, up to 150 entries at once, use the reference checker with FreeCitation PRO.

For developers

The server speaks MCP over Streamable HTTP and answers with JSON, without sessions or an event stream. It accepts protocol versions 2024-11-05 to 2025-11-25. Both tools carry read only annotations and return structured content next to the text. A minimal call:

curl

curl -s https://freecitation.org/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"cite_source","arguments":{"source":"10.1038/nature14539","style":"APA 7th"}}}'

Questions

Why connect a citation tool to an AI assistant?

Because assistants write references from memory, and memory is where invented citations come from. With FreeCitation connected, the assistant can look a DOI up in Crossref or an ISBN up in Open Library and format the real record, and it can check a reference list before you hand it in.

Does it cost anything?

No. The server is free to use without a key, with fair use limits per connection: 120 citations and 30 reference checks an hour, and up to 5 references in each check. Whole reference lists of up to 150 entries are checked on the website with FreeCitation PRO.

What happens when no record is found?

The tool says so and returns no citation. It does not ask an AI model to guess, and its instructions tell the assistant not to fill in missing details itself. Ask your assistant to request the DOI or ISBN from you, or use the manual form on freecitation.org.

What does FreeCitation keep from my requests?

For each call: the tool used, whether a record was found, the name the connecting app gives itself and a one way hash of its IP address, which the hourly limits need. The DOIs, links and reference lists you send are looked up and not stored.

Citations your assistant cannot make up