NARA Catalog

nara-catalog-mcp

An MCP server for genealogical research in the US National Archives Catalog. Find an ancestor's pension file, service record or census page, read what machines and volunteers have transcribed from it, and fetch the page images you will cite. It also searches NARA's Access to Archival Databases (AAD), which the Catalog cannot reach: the NUMIDENT's Social Security applications and deaths, the WWII Army enlistment cards, and the 1820–1912 ship passenger lists among them.

It works the way a careful genealogist does. A catalogue description is a finding aid, and OCR text, transcriptions and tags are somebody else's reading of the page: all of them are leads. The page image is the source. The tools say which is which, and the server tells the model to read the image before citing it.

Nothing here writes to the Catalog, and nothing here keeps a family tree. The server finds and reads records; what you conclude from them belongs in your genealogy software, or in a family-tree MCP server running alongside this one.

The tools work on any record the Catalog describes, so a historian or a journalist can use them too. The examples throughout are about tracing people.

This is an independent project. It is not affiliated with, endorsed by, or supported by the National Archives and Records Administration.

Tools

The server publishes 21 tools. Twenty only read, and are annotated read-only for the client. One, download_page_image, writes a new file to local disk; it never overwrites one.

Finding a record

Tool	Purpose
search_records	Search by title or full text. Returns totals plus compact summaries: NAID, hierarchy, holding unit, date coverage, image count. Each series names its creator, the office that made it, which tells apart the many series sharing a title.
search_records_advanced	The same search with the filters that narrow a common name: date range, record group, collection, ancestor NAID, level of description, microfilm publication number, local identifier, any control number, Congress number, reference unit, creator, person or organisation, place, type of materials, recurring date, digitised-only, "has transcriptions/tags/comments", exact matching of identifiers, search_after cursor paging past 10,000 hits, and each hit's OCR text (NARA's and partners') folded in on request.
browse_children	The immediate children of a node: record group to series to file unit to item. Walk down from a series you trust.

Reading a record

Tool	Purpose
get_record	Read one record in full by NAID: scope and content note, hierarchy, reference units, every page image with its object id.
get_record_images	Page images in page order, each with its object id and URL — the evidence to read before citing.
download_page_image	Save one page to a new local file, by page number or by the object id an OCR or transcription entry names. The media host is open, so this spends no API quota.
get_online_availability	Where else the record is published online, including by commercial partners.
get_partner_digital_objects	Digital object ids a commercial partner (Ancestry among them) has matched to this NAID. An empty list is the common answer.

What machines and other people read in it

Everything in this group is somebody else's reading of the document. It tells you which page to open. It does not tell you what the page says.

Tool	Purpose
get_extracted_text	OCR text extracted from the page images, per digital object, with who produced it, and the object total and next results page when a file runs longer than one call.
get_transcriptions	Citizen transcriptions — how you get into a handwritten pension file that OCR cannot touch.
get_tags	Citizen tags, which on genealogical records are usually the names of the people inside the file.
get_comments	Other researchers' notes on the record.

Searching the documents rather than the catalogue

Tool	Purpose
search_by_contribution_text	Search transcriptions, tags, comments and OCR text — and get full record summaries back.
search_transcriptions	Find records whose transcribed text mentions a name or phrase.
search_tags	Find records carrying a tag, exactly or by word.
search_extracted_text	Find records whose partner-contributed extracted text matches.
search_comments	Find records other researchers have commented on.

NARA's Access to Archival Databases (AAD)

AAD serves a selection of NARA's electronic records as searchable tables. Each row is a database entry an agency clerk typed from a record: a transcription or index entry, not the record, and cited as an electronic record. These tools need no key and spend none of the Catalog allowance.

Tool	Purpose
aad_list_series	The series in an AAD category (genealogy by default), each with its files and their ids. A search runs on one file.
aad_search	Search one file by free text over the whole row and by named fields; 50 rows a page, each with its record id.
aad_get_record	One row in full, every coded value with its meaning, and a citation in NARA's recommended form with the date retrieved.

Housekeeping

Tool	Purpose
api_budget	Live calls and cache hits this session, the month's live calls from a ledger beside the cache, and what remains of the key's monthly allowance.

Setup

You need Python 3.11 or later, uv, and a Catalog API key. Request a key from the Catalog API team via the API documentation; the default allowance is 10,000 calls per month.

There are two ways to run the server.

Without cloning. uvx fetches it from PyPI and runs it in one step, and caches the result:

NARA_API_KEY=your-key uvx nara-catalog-mcp

From a clone, which is what you want if you will change it:

git clone https://github.com/ianderso/nara-catalog-mcp
cd nara-catalog-mcp
uv sync
cp .env.example .env      # then put your key in it
uv run nara-catalog-mcp   # stdio server, usually launched by the client

Either way the server speaks MCP over stdio, so you will normally let an MCP client start it rather than run it by hand.

Claude Desktop

Without cloning:

{
  "mcpServers": {
    "nara": {
      "command": "uvx",
      "args": ["nara-catalog-mcp"],
      "env": { "NARA_API_KEY": "your-key" }
    }
  }
}

From a clone (the env block can be dropped if the key is in the clone's .env):

{
  "mcpServers": {
    "nara": {
      "command": "uv",
      "args": ["--directory", "/path/to/nara-catalog-mcp", "run", "nara-catalog-mcp"],
      "env": { "NARA_API_KEY": "your-key" }
    }
  }
}

A desktop app does not always inherit your shell's PATH. If the server fails to start because uv or uvx cannot be found, give the full path that which uvx prints as the command.

Claude Code

claude mcp add nara --env NARA_API_KEY=your-key -- uvx nara-catalog-mcp

or, from a clone whose .env holds the key:

claude mcp add nara -- uv --directory /path/to/nara-catalog-mcp run nara-catalog-mcp

Configuration

All settings come from the environment. A .env file in the directory the server starts in supplies any that the environment does not; with uv --directory that is the clone. Only that directory is read — not its parents, and not the directory the package is installed in.

Variable	Meaning
NARA_API_KEY	Your Catalog API key. Required by the Catalog tools; the AAD tools need none.
NARA_CACHE_DIR	Response cache directory. Default ~/.cache/nara-catalog-mcp.
NARA_TIMEOUT	HTTP timeout in seconds. Default 60.
NARA_MONTHLY_CALL_BUDGET	Calls per month the key allows, reported by api_budget. Default 10000.

A missing key, or an unusable value, is reported on the first tool call as a not_configured result naming the variable.

The call budget

A Catalog key is capped per month, and a sweep across many names will exhaust it faster than expected. Every successful response is cached on disk, keyed by endpoint and query, so repeating a call costs nothing. Live calls are also written to a ledger, budget.json beside the cache, so api_budget reports the month's spend across sessions as well as this session's live calls and cache hits. A rejected call counts as live, since it reached the API. The ledger sees one machine and one cache directory; the Catalog's own count is the authority.

The cache never expires. Pass refresh=true to get_record, get_record_images, get_extracted_text, get_transcriptions, get_tags or get_comments to re-read one answer from the Catalog: that spends one call and replaces the cached copy. New transcriptions and tags arrive over time, and a file that was paper-only can be digitised, so a cached "nothing here" is the answer most worth refreshing. Deleting NARA_CACHE_DIR still works, and also resets the month's ledger.

Searching past the first 10,000 hits

page stops working beyond 10,000 results, which a common surname passes. search_records_advanced reports a paging_note when you hit that boundary; either narrow the search or re-run it with search_after="*" and follow the next_search_after value from each response.

How a search behaves

title matches words in the record title and is the precise option — case files are usually titled with the person's name. query searches the full description: broader, noisier, and worth reaching for only when a title search finds nothing.

Results come back as summaries rather than whole records. A raw Catalog record is large and mostly irrelevant to the decision you are making, which is whether this record is worth opening.

Searching AAD

AAD has no API, so aad_* read its web pages the way a browser does, and parse them. That shapes how they behave:

• One file at a time. A big series is split into files, and a search runs on one. The NUMIDENT is split by entry type (application, claim, death) and by surname range, so aad_list_series comes first.
• Fields by name. fields={"LAST NAME": "PRESLEY", "DATE OF BIRTH (YEAR)": "1930-1935"}. A field AAD stores as a code, such as a state or a country, cannot be searched by name: put its meaning in query, which matches the whole row, code meanings included.
• Slow on purpose. One request at a time, at least two seconds apart, and a search usually takes two requests because AAD answers first with a "Please Wait" page. Answers are cached for seven days, under NARA_CACHE_DIR/aad; refresh=true on aad_get_record fetches a row again.
• Record ids are not stable. NARA reloads files, and a reload can renumber the rows. Search again rather than reuse an old id, and cite a row by its fields, its file and its series.
• A row is not the record. It was keyed from an SS-5, a punch card or a manifest, with the keying errors that brings, and no file holds everyone. The NUMIDENT has entries only for people with a verified death or born before 1908, and its death file omits state-reported deaths. Each answer carries AAD's own notice for the file, and a NUMIDENT answer says what that file leaves out.

Notes

• A description is not evidence. It summarises a file; it says nothing about what any individual page contains. Read the images before citing.
• Neither is OCR, and neither is a transcription. get_extracted_text is a machine reading a scan of handwriting; get_transcriptions is one volunteer's typing, unreviewed. Both are the fastest way to find the page that matters, and neither is a source. Open the image and cite that.
• Record the NAID. It is the stable identifier that makes a citation refindable.
• Not every record is digitised. image_count: 0 means the description exists but the pages are not online — the reference_units field tells you which archive holds the paper.
• Open is not unrestricted. The media host needs no key, and most of NARA's holdings are in the public domain, but not all: some descriptions record use restrictions. Check before republishing an image.

Deliberately not here

The Catalog API can post tags and comments and put transcriptions. This server does not, and will not by default: a contribution publishes under whoever's key is configured, and nothing here can take it back.

Security

• The key is read from the environment, sent only to catalog.archives.gov as the x-api-key header, and never sent to the media host or to AAD. It is not written to the response cache.
• The AAD client reads one host. A request hook refuses any host but aad.archives.gov, so nothing a model passes in can make it fetch another site. It identifies itself as Mozilla/5.0 (compatible; nara-catalog-mcp/<version>; +<this repository>), the form crawlers such as Googlebot use. AAD's load balancer answered 403 to the plain nara-catalog-mcp/<version> form when it was tried; see docs/API-NOTES.md.
• Contributions are untrusted text. Tags, comments and transcriptions are written by members of the public and reach the model verbatim, so one could contain instructions aimed at it. The server's instructions tell the model to treat that text as material to weigh, never as instructions; the model is still the one deciding, so review what it proposes to do.
• download_page_image writes files. It creates a new file wherever the server's user can write, and refuses to overwrite an existing one — so a mistaken or injected path cannot destroy anything. It is annotated as not read-only, so a client can ask before each call.

To report a vulnerability, see SECURITY.md.

Development

uv sync --extra dev
uv run pytest                # mocked with respx; no API key needed
uv run ruff check .
uv run ruff format --check .
uv run python -m tests.live_check   # needs a key: asks the Catalog what the mocks cannot

The live check asks the Catalog what the mocks cannot: where the two text flags put their text, which search parameters the server does not send, and whether search summaries still name each series' creator. It also asks AAD whether it still admits the client and whether the parsers still read its pages. Run it after a change on either side; a difference shows up in its output.

See CONTRIBUTING.md for how the suite is organised and what a change is expected to carry.

API notes

The published OpenAPI spec is unreliable in specific, repeatable ways — wrong required flags, maximum used where maxLength is meant, and two conflicting definitions of the pagination cursor. Corrections verified against the live Catalog are in docs/API-NOTES.md. Why the server is shaped the way it is, what is out of scope by decision, and how the test suite is built are in docs/DESIGN.md.

License

MIT.