Historical Investigator

A beginner-friendly Model Context Protocol (MCP) server that searches historical records from the Library of Congress APIs.

Built with TypeScript, Node.js, the official @modelcontextprotocol/sdk, and zod for input validation.

Setup

npm install
npm run build

Running the server

The server communicates over stdio (standard for MCP):

npm start

Cursor / MCP client configuration

Add this to your MCP settings (for example in Cursor):

{
  "mcpServers": {
    "historical-investigator": {
      "command": "node",
      "args": ["/absolute/path/to/historical-investigator-mcp/dist/index.js"]
    }
  }
}

Replace the path with your local clone of this project.

Tools

1. search_historical_newspapers

Search historical newspaper records from Chronicling America via the Library of Congress API.

Parameter	Type	Required	Description
query	string	yes	Search keywords
state	string	no	US state name or abbreviation
dateStart	string	no	Start date (YYYY-MM-DD)
dateEnd	string	no	End date (YYYY-MM-DD)
limit	number	no	Max results (1–100, default 20)

Example prompt: “Search Chronicling America for articles about the San Francisco earthquake in California between 1906-04-01 and 1906-04-30.”

Uses the Chronicling America collection endpoint with:

• q — keyword search
• fa=location:{state} — state filter (e.g. location:california)
• start_date / end_date — date range (YYYY-MM-DD)
• c — result limit
• fo=json — JSON response

The response includes a requestUrl field with the exact LOC API URL used, which helps with debugging.

Date filtering limitation: The LOC API accepts start_date and end_date, but results are not always strictly limited to that range. You may see newspaper pages from nearby dates (or later years) when the search terms appear in OCR text. If you need an exact date window, check each result’s date field and filter client-side.

---

2. get_newspaper_item

Fetch metadata for a specific LOC item or resource.

Parameter	Type	Required	Description
itemIdOrUrl	string	yes	Item ID (e.g. 2014717546) or full loc.gov URL

Example prompt: “Get metadata for LOC item 2014717546.”

---

3. fetch_page_ocr_text

Download raw OCR plain text from a URL (often found in item metadata).

Parameter	Type	Required	Description
ocrTextUrl	string	yes	URL to the OCR text file

Example prompt: “Fetch the OCR text from this URL: …”

Returns plain text. Errors are handled safely and reported back to the client.

---

4. search_prints_and_photographs

Search prints and photographs in the LOC collections.

Parameter	Type	Required	Description
query	string	yes	Search keywords
limit	number	no	Max results (1–100, default 20)

Uses: https://www.loc.gov/photos/ with fo=json.

---

5. search_maps

Search map records in the LOC collections.

Parameter	Type	Required	Description
query	string	yes	Search keywords
limit	number	no	Max results (1–100, default 20)

Uses: https://www.loc.gov/maps/ with fo=json.

---

6. search_manuscripts

Search manuscript records in the LOC collections.

Parameter	Type	Required	Description
query	string	yes	Search keywords
limit	number	no	Max results (1–25, default 10)

Uses: https://www.loc.gov/manuscripts/ with fo=json.

Returns trimmed fields: title, date, contributor, description, subjects, and item link.

---

7. search_audio_recordings

Search audio recordings in the LOC collections.

Parameter	Type	Required	Description
query	string	yes	Search keywords
limit	number	no	Max results (1–25, default 10)

Uses: https://www.loc.gov/audio/ with fo=json.

Returns trimmed fields: title, date, contributors, description, subjects, and item link.

---

8. search_film_and_video

Search film and video records in the LOC collections.

Parameter	Type	Required	Description
query	string	yes	Search keywords
limit	number	no	Max results (1–25, default 10)

Uses: https://www.loc.gov/film-and-videos/ with fo=json.

Returns trimmed fields: title, date, contributors, description, subjects, and item link.

---

9. get_item_resources

Fetch a specific LOC item or resource and return digital files when available.

Parameter	Type	Required	Description
itemIdOrUrl	string	yes	Item ID, resource path, or full loc.gov URL

Returns title, date, item link, resources/files/images/OCR links when present. If nothing is digitized, returns a helpful message.

---

10. compare_historical_sources

Compare two LOC records side by side using metadata only (no AI summarization).

Parameter	Type	Required	Description
itemIdOrUrl1	string	yes	First item ID or full loc.gov URL
itemIdOrUrl2	string	yes	Second item ID or full loc.gov URL

Returns both records (title, date, location, contributors, subjects, description, link) plus a comparison object with same_year, shared_subjects, and source_types.

Project structure

historical-investigator-mcp/
├── src/
│   └── index.ts      # MCP server and LOC API helpers
├── package.json
├── tsconfig.json
├── README.md
└── .gitignore

API notes

• All LOC requests use fo=json for JSON responses.
• Newspaper searches use q, optional fa=location:..., and optional start_date / end_date on the Chronicling America collection endpoint.
• Photo and map searches use the /photos/ and /maps/ format endpoints with q and c.
• Manuscript, audio, and film searches use /manuscripts/, /audio/, and /film-and-videos/ with trimmed result fields.
• get_item_resources and compare_historical_sources fetch item metadata with fo=json.
• No API key is required for the public LOC JSON/YAML API.
• State values can be full names (California) or abbreviations (CA); both are normalized to LOC location facets.

License

MIT