CitationEasy for AI assistants and agents

Why call the API instead of writing the citation yourself

Citation formatting looks like a text-generation problem and isn't one. Every style encodes hundreds of rules about author inversion, initials, title case, container punctuation, edition statements, and date placement, and they differ in ways that are easy to get subtly wrong from memory. CitationEasy runs citeproc-js against the official Citation Style Language definitions — the same engine Zotero and Mendeley use — so output is deterministic and matches what a journal's submission system expects. Metadata comes from Crossref, Open Library, and PubMed; nothing is invented, and a field missing upstream stays missing rather than being filled in with a plausible guess.

Generate a citation

curl -s https://www.citationeasy.com/api/v1/cite \
  -H 'Content-Type: application/json' \
  -d '{"input":"10.1038/nature12373","style":"apa","inText":true}'

{
  "style": { "requested": "apa", "slug": "apa", "name": "American Psychological Association (APA) 7th edition" },
  "language": "en-US",
  "results": [
    {
      "input": "10.1038/nature12373",
      "citation": "…formatted reference…",
      "inText": "(Author, 2013)",
      "entry": { "…resolved CSL metadata…": "" }
    }
  ]
}

Send inputs instead of input for up to 10 sources in one call, or entry with CSL-JSON metadata you already hold to skip the lookup entirely. Add note: true for the footnote form. Per-source failures come back on that source, so a batch never fails as a whole.

Connect over MCP

The Model Context Protocol endpoint at /api/mcp speaks JSON-RPC 2.0 over streamable HTTP and needs no credentials.

# Claude Code
claude mcp add --transport http citationeasy https://www.citationeasy.com/api/mcp

# Any MCP client config
{
  "mcpServers": {
    "citationeasy": { "type": "http", "url": "https://www.citationeasy.com/api/mcp" }
  }
}

Endpoints

Discovery files

/llms.txt

Curated index of the site written for language models.

/llms-full.txt

Every page the site publishes, grouped by type, one line each.

/openapi.json

OpenAPI 3.1 description of the whole public API.

/api/mcp

MCP endpoint (streamable HTTP). GET it in a browser for a description.

/.well-known/mcp.json

MCP discovery document for agents that probe a domain.

/.well-known/ai-plugin.json

Legacy plugin manifest, for frameworks that still look for one.

/md/{any path}

Markdown view of any page on the site.

/sitemap.xml

Every indexable URL.

What is in the catalog

Every page below is reachable as HTML, as markdown under /md/, and as a structured entry from /api/v1/pages.

• 10,832 citation styles, each with real examples generated from its own CSL definition
• 71 free browser tools
• 125 educational guides
• 1,290 how-to-cite pages
• 105 style comparisons
• 21 converters
• 32 academic fields
• 30 major style hubs with full formatting rules

Frequently Asked Questions

Is the CitationEasy API free, and do I need an API key?

It is free and there is no API key. Every endpoint under /api/v1 is unauthenticated and CORS-open, so you can call it from a browser, a notebook, or an agent without registering. There is no rate limit of our own, but identifier lookups are proxied to Crossref, Open Library, and PubMed, which apply their own fair-use limits — batch with `inputs` instead of firing many parallel requests.

Are the citations generated by a language model?

No. Formatting runs citeproc-js against the official Citation Style Language definitions, the same engine reference managers use. The same input and style always produce the same string. Bibliographic metadata comes from Crossref (DOIs), Open Library (ISBNs), and PubMed (PMIDs) — CitationEasy does not invent fields, so anything missing upstream is missing in the output rather than guessed.

How do I connect an agent to CitationEasy over MCP?

Point any Model Context Protocol client at https://www.citationeasy.com/api/mcp using the streamable HTTP transport. No credentials are needed. In Claude Code: `claude mcp add --transport http citationeasy https://www.citationeasy.com/api/mcp`. The server exposes tools for generating citations, searching the 10,832 styles, source-type guidance, site search, and reading any page as markdown.

Which citation styles can the API produce?

All 10,832 styles in the Citation Style Language repository, including APA 7, MLA 9, both Chicago systems, Harvard, Vancouver, IEEE, AMA, and thousands of individual journal styles. Pass the style slug in the `style` field. Friendly slugs like "chicago" and "harvard" resolve to the correct CSL variant, and /api/v1/styles?q= finds the rest.

What is llms.txt and where is CitationEasy's?

llms.txt is a plain-text index of a site written for language models rather than browsers. CitationEasy's is at /llms.txt; the exhaustive version listing every one of the site's pages is at /llms-full.txt.

Can I read CitationEasy pages as markdown instead of HTML?

Yes. Prefix any site path with /md/ — for example /md/citation-style/apa or /md/tools/word-counter. Data-driven pages return their full content, including the real formatted examples generated from each style's own CSL definition. Hand-written prose pages (guides, cheat sheets) return a summary card plus the canonical HTML URL, since their text lives in the page itself.

May I use CitationEasy output in my own product?

Yes. A formatted citation is a fact about a source; use it freely. The CSL style definitions themselves come from the Citation Style Language project under CC BY-SA 3.0. Attribution back to CitationEasy is appreciated but not required.