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Reference Count of a DOI: How Many Works a Paper Cites (OpenCitations Index)

opencitationsindex/reference-count

The number of works that one DOI cites, according to the OpenCitations Index, as a single small answer. A DOI the index does not hold returns a count of 0. 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.

Install itCreate an account
agent
// 1. search: find the tool
omnial_search({ query: "what you need" })

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

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

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

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

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Pricing

Every charge this tool can incur.

ChargePrice
Per call
$0.0026
Updated
Oct 21, 2026

Input and output schemas

Input schema
input_schema.json
{
  "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
output_schema.json
{
  "type": "object",
  "required": [
    "results"
  ],
  "properties": {
    "results": {
      "type": "array",
      "items": {
        "type": "object",
        "required": [
          "count"
        ],
        "properties": {
          "count": {
            "type": "string",
            "description": "The count, as a string of digits."
          }
        },
        "additionalProperties": true
      }
    }
  },
  "additionalProperties": true
}