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 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 18 tools. Seventeen 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

Reading a record

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.

Searching the documents rather than the catalogue

Housekeeping

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.

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.

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. It is not written to the response cache.
• 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, and which search parameters the server does not send. 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.