LC Subject Headings Autocomplete (Library of Congress Subject Heading Suggest)

locidlinked/subject-heading-suggest

Autocompletes Library of Congress Subject Headings: give the start of a term and get the matching authorised headings, each with its URI, variant labels and broader terms, ten at a time in alphabetical order with the total match count. A term that matches nothing returns an empty list. Library of Congress data, a public domain data set passed through unmodified and served by Omnial; not an official Library of Congress 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 $5.

Data source

Library of Congress

Data from the Library of Congress Linked Data Service (id.loc.gov), made available by the Library of Congress as a public domain data set. Served by Eden Engine; not an official Library of Congress 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: "locidlinked/subject-heading-suggest" })

// 3. learn: read the usage guide at runtime
omnial_learn({ tool: "locidlinked/subject-heading-suggest" })

// 4. run: price the exact call first, then run it
omnial_execute({ tool: "locidlinked/subject-heading-suggest", input: { /* see input_schema */ }, dry_run: true })
omnial_execute({ tool: "locidlinked/subject-heading-suggest", 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 20, 2026

Input and output schemas

Input schema

input_schema.json

{
  "type": "object",
  "required": [
    "q"
  ],
  "properties": {
    "q": {
      "type": "string",
      "maxLength": 200,
      "minLength": 1,
      "description": "The start of the heading to look for, for example cats or climate. Matching is left-anchored: headings that begin with this text are returned."
    }
  },
  "additionalProperties": false
}

Output schema

output_schema.json

{
  "type": "object",
  "required": [
    "hits"
  ],
  "properties": {
    "q": {
      "type": "string",
      "description": "The query as received."
    },
    "hits": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "uri": {
            "type": "string",
            "description": "The heading's identifier URI."
          },
          "more": {
            "type": "object",
            "description": "Extra detail: notes, variant labels, broader terms, collections and last-modified date.",
            "additionalProperties": true
          },
          "token": {
            "type": "string",
            "description": "The identifier at the end of the URI."
          },
          "aLabel": {
            "type": "string",
            "description": "The authorised heading."
          },
          "vLabel": {
            "type": "string",
            "description": "The variant form that matched, or empty."
          },
          "suggestLabel": {
            "type": "string",
            "description": "The text shown for the match. Ends with (USE ...) when a variant form matched."
          }
        },
        "additionalProperties": true
      },
      "description": "Matching headings. Empty when nothing matches."
    },
    "count": {
      "type": "integer",
      "description": "Total number of matching headings."
    },
    "start": {
      "type": "integer",
      "description": "Position of the first returned hit."
    },
    "pagesize": {
      "type": "integer",
      "description": "Number of hits returned per page."
    },
    "directory": {
      "type": "string",
      "description": "The vocabulary that was searched."
    },
    "searchtype": {
      "type": "string",
      "description": "How the query is matched, left-anchored."
    },
    "sortmethod": {
      "type": "string",
      "description": "How hits are ordered, alpha."
    }
  },
  "description": "The Library of Congress suggestions response: the echoed query, the total match count, the paging fields and the first page of matching headings.",
  "additionalProperties": true
}