Works That Cite a DOI: Incoming Citations (OpenCitations Index)
opencitationsindex/citations
Lists the citations that point at one DOI in the OpenCitations Index: for each, the citation id (OCI), the citing and cited works with their DOI, PubMed, OpenAlex and OMID identifiers, the date, the time between the two publications and journal and author self-citation flags. Returns at most the first 500 citations and reports the total; a DOI cited more than about 30,000 times exceeds the response size limit and fails, so use the citation count tool for those. OpenCitations data (CC0), passed through unmodified and served by Eden Engine; not an official OpenCitations product.
Price
$0.0026 per call
You pay the price shown. If a call turns out to cost more than its quote, you pay the actual price, capped at twice the quote. No monthly minimum. Top-ups start at $0.50.
Data source
OpenCitations (opencitations.net)
Citation data from the OpenCitations Index (opencitations.net), published under the CC0 public domain waiver. Served by Eden Engine; not an official OpenCitations product.
Use it
Five steps: search, inspect, learn, run, settle. No per-tool setup; your agent reaches this tool through the meta-tools it already has.
Connect once and your AI can find and run this tool, and any other it needs.
// 1. search: find the tool
omnial_search({ query: "what you need" })
// 2. inspect: price and input schema
omnial_inspect({ tool: "opencitationsindex/citations" })
// 3. learn: read the usage guide at runtime
omnial_learn({ tool: "opencitationsindex/citations" })
// 4. run: price the exact call first, then run it
omnial_execute({ tool: "opencitationsindex/citations", input: { /* see input_schema */ }, dry_run: true })
omnial_execute({ tool: "opencitationsindex/citations", input: { /* ... */ } })
// 5. settle: the call is charged when it finishes, nothing to doNot connected yet? Point your MCP client at https://mcp.eden-engine.com/mcp, then copy a config for your client.
Pricing
Every charge this tool can incur.
| Charge | Price |
|---|---|
Per call | $0.0026 |
- Updated
- Oct 21, 2026
Input and output schemas
Input schema
{
"type": "object",
"required": [
"doi"
],
"properties": {
"doi": {
"type": "string",
"pattern": "^10\\.[0-9]{4,9}/[^\\s?#]{1,200}$",
"description": "A DOI without the doi: prefix, for example 10.1186/1756-8722-6-59."
}
},
"additionalProperties": false
}Output schema
{
"type": "object",
"required": [
"total",
"returned",
"truncated",
"citations"
],
"properties": {
"total": {
"type": "integer",
"description": "How many citations OpenCitations returned for the DOI."
},
"returned": {
"type": "integer",
"description": "How many of them are in `citations` (at most 500)."
},
"citations": {
"type": "array",
"items": {
"type": "object",
"properties": {
"oci": {
"type": "string",
"description": "The citation's Open Citation Identifier."
},
"cited": {
"type": "string",
"description": "Space-separated identifiers of the cited work."
},
"citing": {
"type": "string",
"description": "Space-separated identifiers of the citing work (omid, doi, pmid, openalex)."
},
"creation": {
"type": "string",
"description": "Date the citation was created (the citing work's publication date), YYYY, YYYY-MM or YYYY-MM-DD."
},
"timespan": {
"type": "string",
"description": "ISO 8601 duration between the two publication dates, for example P2Y1M11D."
},
"author_sc": {
"type": "string",
"description": "yes when the two works share an author (author self-citation), else no."
},
"journal_sc": {
"type": "string",
"description": "yes when citing and cited works share a journal (journal self-citation), else no."
}
},
"additionalProperties": true
},
"description": "The citations, in the order OpenCitations returns them."
},
"truncated": {
"type": "boolean",
"description": "True when `total` is above 500 and `citations` holds only the first 500."
}
},
"additionalProperties": false
}