census-mcp
U.S. Census data by ZIP code, inside your agent. An MCP
server that lets an LLM look up income, demographics, housing, and education for any ZIP —
built on Anthropic's official mcp Python SDK.
All tools are read-only. Data is the U.S. Census Bureau's American Community Survey (ACS)
5-year release — bulk-downloaded once into a local store, then served offline. A free
Census API key is required for the one-time download.
Status: published (v0.1.2) — uvx mcpwright-census (PyPI) and listed in the official MCP
Registry as io.github.mcpwright/census-mcp. All 8 tools below are live and unit-tested, verified
end-to-end against the live ACS 5-year release (vintage 2024 at the time of writing — the
server auto-detects the latest). Part of the
mcpwright suite.
Tools
| Tool | What it does |
|---|
lookup_zip(zip_code) | Confirm a ZIP maps to a Census ZCTA; returns name, total population, and the ACS vintage. |
get_income(zip_code) | Median household income, per-capita income, total households, and the % of households earning $200k+. |
get_demographics(zip_code) | Total population and median age. |
get_housing(zip_code) | Median home value, median gross rent, occupied units, and % owner-occupied. |
get_education(zip_code) | Of adults 25+, the % with a bachelor's degree or higher and the % with a graduate/professional degree. |
compare_zips(zips, metric) | Rank several ZIPs by one metric (income, age, home value, attainment, …), highest first. |
get_acs_variable(zip_code, variable) | Escape hatch: the raw value of any stored ACS variable, by code or friendly name. |
find_zips(place, state=None) | Reverse lookup: the ZIPs that fall within a city/town/CDP, ranked by how much of each ZIP's land lies in the place. |
ZIP ≈ ZCTA (ZIP Code Tabulation Area): they mostly coincide, but ~2% of ZIPs (PO-box-only /
non-residential) have no ZCTA and will return an error. All ACS figures are 5-year estimates.
find_zips is the reverse direction (place → ZIPs). It's approximate: ZCTAs don't nest inside
places, so a ZIP can span several places and vice versa — read each match's coverage_pct and
pass a state to disambiguate same-named places (e.g. Cambridge, MA vs OH). It's built on the
public 2020 Census ZCTA-to-Place relationship file (2020 geography; no API key needed for it).
Install
Requires Python 3.12+ and a free Census API key
(set CENSUS_API_KEY). The PyPI package is mcpwright-census; the command, server, and tools
are all "census".
export CENSUS_API_KEY=your-free-key
uvx mcpwright-census setup # one-time: bulk-download the ACS dataset into a local store
Claude Code
claude mcp add census -e CENSUS_API_KEY=your-free-key -- uvx mcpwright-census
Claude Desktop
Add to claude_desktop_config.json:
{
"mcpServers": {
"census": {
"command": "uvx",
"args": ["mcpwright-census"],
"env": { "CENSUS_API_KEY": "your-free-key" }
}
}
}
First run downloads the full ACS dataset (~33k ZCTAs) into a local SQLite store under
your OS cache dir, so every later lookup is instant and offline. Run mcpwright-census setup
ahead of time, or let the server download lazily on first use. mcpwright-census refresh
re-pulls when a new ACS vintage is published. Override the store location with
CENSUS_MCP_STORE.
Develop
git clone https://github.com/mcpwright/census-mcp && cd census-mcp
uv sync
uv run pytest -v # tests (mocked Census + seeded SQLite)
uv run ruff check src/ && uv run ruff format --check src/ # lint + format
uv run mypy # type checking
uv run mcp dev src/census_mcp/server.py # poke the tools in the MCP Inspector
Roadmap
Privacy
census-mcp runs entirely on your machine and collects, stores, or transmits no personal
data — no accounts, no tracking, no telemetry. Its only outbound requests go to the public
U.S. Census Bureau to download public data: api.census.gov for the ACS dataset (using
your own CENSUS_API_KEY), and www2.census.gov for the place-lookup file used by
find_zips (no key needed). The key is read from your environment and is never logged or sent
anywhere else. These downloads happen during setup/refresh (or lazily on first use); after
that, lookups are served from a local store with no further network calls. The downloaded data
lives under your OS cache directory (public reference data only) and can be deleted at any time.
Full policy: https://mcpwright.com/privacy
Questions & feedback
- Questions, ideas, or "could it do X?" → Discussions
- Bugs & concrete feature requests → Issues
Contributions welcome.
Part of mcpwright · built by Devender Gollapally
