Census

The official US Census Bureau data: decennial census, American Community Survey (ACS), economic census, population estimates, housing characteristics, geographic boundaries. National, state, county, place, tract, block-group, and ZCTA-level. Free, no key required for public datasets.

Part of Pipeworx — an MCP gateway connecting AI agents to 1394+ live data sources.

Why this matters for AI agents

Demographics, housing characteristics, economic activity, geographic identifiers — Census is the authoritative source. If an agent is computing per-capita rates, comparing metros, looking up population, or working with FIPS codes, this is where it goes.

Common flows:

• Population for an area. ACS 1-year or 5-year estimates by state/county/place.
• Housing characteristics. Median home value, occupancy, units, age — all in ACS.
• Geographic ID lookup. Place name → FIPS code → boundary geometry.
• Economic Census every 5 years for industry-level economic activity.

Pair with FRED for time-series macro and BLS for labor.

Auth

Most Census APIs are free and unauthenticated, with light rate limits (~500 calls/day per IP). For higher rates, get a key at https://api.census.gov/data/key_signup.html and pass via _apiKey.

Datasets worth knowing

Dataset	Cadence	Geography
Decennial Census (PL, DHC)	10-year	Block-level and up
ACS 5-year	Annually-rolling	Tract/BG (5-year smoothing)
ACS 1-year	Annually	Places ≥65k population
Population Estimates Program (PEP)	Annually	County-level
Economic Census	5-year	Industry × geography

ACS 5-year is what you usually want for current demographics — it's available at finer geographies than 1-year and updates yearly with rolling 5-year smoothing.

Common pitfalls

• Year-of-coverage vs release year. ACS 5-year 2018-2022 was released in 2023. Don't conflate.
• Margins of error. ACS includes MOE for every estimate. At small geographies (block group, small tract), MOEs can be larger than the estimate. Always carry MOE through to the user.
• Geography hierarchy. State (01) → County (01001) → Tract (01001020100) → Block Group. The 11-digit tract code is state(2) + county(3) + tract(6).
• Place vs MSA. "Denver" can mean the City and County of Denver, OR the Denver-Aurora-Lakewood Metropolitan Statistical Area (very different boundaries and populations). Disambiguate per use case.
• Population estimates lag the decennial. Between censuses, PEP estimates are extrapolated and revised. The Census Bureau revises previous PEPs each year as they reconcile with births/deaths/migration data.

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "census": {
      "url": "https://gateway.pipeworx.io/census/mcp"
    }
  }
}

Or connect to the full Pipeworx gateway for access to all 1394+ data sources:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English:

ask_pipeworx({ question: "your question about Census data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides
• pipeworx.io

License

MIT