Citation Record by OCI: Citing Work, Cited Work, Date, Timespan (OpenCitations Index)

opencitationsindex/citation

Looks up one citation in the OpenCitations Index by its Open Citation Identifier (OCI, two numbers joined by a dash): the citing and cited works with their DOI, PubMed, OpenAlex and OMID identifiers, the date, the time between the two publications and self-citation flags. An OCI the index does not hold returns an empty list. OpenCitations data (CC0), passed through unmodified and served by Eden Engine; not an official OpenCitations product.

activeper callv1

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.

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agent

// 1. search: find the tool
omnial_search({ query: "what you need" })

// 2. inspect: price and input schema
omnial_inspect({ tool: "opencitationsindex/citation" })

// 3. learn: read the usage guide at runtime
omnial_learn({ tool: "opencitationsindex/citation" })

// 4. run: price the exact call first, then run it
omnial_execute({ tool: "opencitationsindex/citation", input: { /* see input_schema */ }, dry_run: true })
omnial_execute({ tool: "opencitationsindex/citation", input: { /* ... */ } })

// 5. settle: the call is charged when it finishes, nothing to do

Not 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

input_schema.json

{
  "type": "object",
  "required": [
    "oci"
  ],
  "properties": {
    "oci": {
      "type": "string",
      "pattern": "^[0-9]{1,20}-[0-9]{1,20}$",
      "description": "An Open Citation Identifier without the oci: prefix: two numbers separated by a dash, for example 06101801781-06180334099."
    }
  },
  "additionalProperties": false
}

Output schema

output_schema.json

{
  "type": "object",
  "required": [
    "results"
  ],
  "properties": {
    "results": {
      "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
      }
    }
  },
  "additionalProperties": true
}