civic-library-mcp

An MCP server that gives AI agents clean, token-efficient access to US civic & property data — geocoding, census tracts, Opportunity Zones, ACS demographics, and FEMA flood zones — sourced entirely from free federal open data.

No scraping, no paid keys for the core tools, no proprietary databases. Just the official sources (U.S. Census Bureau, U.S. Treasury CDFI Fund, FEMA), wrapped in a small set of well-described tools that return compact JSON instead of the bloated payloads most data MCPs dump into your context window.

Built for developers working on proptech, real-estate, fintech, civic tech, GIS, and housing research with AI agents.

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Tools

Tool	What it does	API key?
geocode_address	US street address → lat/lng + state, county, and 2020 census tract GEOID	None
lookup_census_tract	lat/lng → the 2020 census tract (with county/state) containing that point	None
check_opportunity_zone	Is this address / point / tract in a designated Qualified Opportunity Zone?	None
get_tract_demographics	ACS 5-Year indicators (income, population, home value, poverty rate, …) for a tract	Free Census key
check_flood_zone	lat/lng → FEMA flood-hazard zone + whether it's a Special Flood Hazard Area	None

Four of the five tools work with zero configuration. Only get_tract_demographics needs a free Census API key (see below).

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Install

Claude Desktop / Cursor / any MCP client

Add to your MCP config (e.g. claude_desktop_config.json):

{
  "mcpServers": {
    "civic-library": {
      "command": "npx",
      "args": ["-y", "civic-library-mcp"],
      "env": {
        "CENSUS_API_KEY": "your-free-census-key-optional"
      }
    }
  }
}

Claude Code

claude mcp add civic-library -- npx -y civic-library-mcp

The CENSUS_API_KEY line is optional — leave it out and four of the five tools still work.

Census API key (only for demographics)

get_tract_demographics calls the U.S. Census ACS Data API, which requires a free key. Get one in ~30 seconds at https://api.census.gov/data/key_signup.html and set it as CENSUS_API_KEY in the server's environment.

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Examples

Check whether a property is in an Opportunity Zone:

// check_opportunity_zone({ "address": "900 Camp St, New Orleans, LA 70130" })
{
  "is_opportunity_zone": true,
  "tract_geoid_2010": "22071013400",
  "designation_type": "Low-Income Community",
  "round": "1.0",
  "authority": "Tax Cuts and Jobs Act of 2017 (26 U.S.C. § 1400Z-1)",
  "resolved_from": "address",
  "source": "U.S. Treasury CDFI Fund (designated 2018-12-14)"
}

Flood risk for a coordinate:

// check_flood_zone({ "latitude": 29.9511, "longitude": -90.0715 })
{
  "flood_zone": "X",
  "zone_subtype": "0.2 PCT ANNUAL CHANCE FLOOD HAZARD",
  "in_special_flood_hazard_area": false,
  "zone_description": "Moderate-to-minimal risk (outside the 1% annual-chance floodplain).",
  "source": "FEMA National Flood Hazard Layer"
}

Tract demographics (needs a key):

// get_tract_demographics({ "tract_geoid": "22071013400",
//   "fields": ["population", "median_household_income", "poverty_rate"] })
{
  "tract_geoid": "22071013400",
  "tract_name": "Census Tract 134, Orleans Parish, Louisiana",
  "acs_dataset": "ACS 5-Year 2023",
  "population": 2276,
  "median_household_income": 41250,
  "poverty_rate": 0.231
}

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A note on correctness: Opportunity Zones use 2010 census tracts

Opportunity Zone designations are keyed to 2010 census tract boundaries, but the default Census geocoder returns 2020 tracts — and tract GEOIDs changed between the two vintages. A naive lookup that matches a 2020 GEOID against the OZ list will silently return wrong answers near any boundary that moved.

check_opportunity_zone handles this correctly: it re-resolves the address/coordinate to its 2010 tract before matching. (You can see the difference — the same address can yield GEOID …980000 from geocode_address and …006202 from check_opportunity_zone.) If you pass tract_geoid directly, it's treated as a 2010 GEOID.

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Data sources & licensing

Data	Source	Notes
Geocoding & census tracts	U.S. Census Bureau Geocoder	Public domain
Opportunity Zones	U.S. Treasury CDFI Fund	Round 1 (2018) designations, 8,764 tracts, bundled
Demographics	U.S. Census ACS 5-Year	Public domain; free key required
Flood zones	FEMA National Flood Hazard Layer	Public domain

All underlying data is U.S. federal open data (public domain). This software is MIT-licensed.

The bundled Opportunity Zone list is regenerated with npm run build:oz.

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Roadmap

• OZ 2.0 — designations under the One Big Beautiful Bill Act (2025) once finalized/published.
• More ACS fields — educational attainment, race/ethnicity, housing tenure, commute.
• County parcel / CAD lookups — added per-county only where the source's terms of use permit automated access.
• Census place & ZIP geographies, FEMA base flood elevations.

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Disclaimer

This tool surfaces public government data for informational purposes. It is not legal, financial, tax, insurance, or investment advice. Opportunity Zone, flood-zone, and demographic determinations should be confirmed against the official source of record before relying on them for any transaction. Data is provided "as is" with no warranty.

Contributing

Issues and PRs welcome — especially additional federal open-data sources and ACS fields. Keep responses compact (token cost is a feature) and every data point attributed to its source.

License

MIT © 2026 Adrian Cisneros