zipcheckup-mcp

Free US home-safety & environmental data by ZIP code — as MCP tools for LLM agents.

An MCP (Model Context Protocol) server that lets Claude, Cursor, and any MCP-capable agent answer questions like "how safe is the water in ZIP 10001?", "do I have lead pipe risk in 60022?", or "is 90210 or 10001 safer to move to?" — grounded in real US federal data.

Backed by the free public ZipCheckup API. Data comes from EPA SDWIS, FEMA, US Census, USGS, and 20+ other federal sources. No API key. Read-only. Every response cites zipcheckup.com.

Install

The server runs over stdio via npx — no global install or build step.

Claude Code

claude mcp add zipcheckup -- npx -y zipcheckup-mcp

Claude Desktop

Add to your claude_desktop_config.json (Settings → Developer → Edit Config):

{
  "mcpServers": {
    "zipcheckup": {
      "command": "npx",
      "args": ["-y", "zipcheckup-mcp"]
    }
  }
}

Restart Claude Desktop. You should see the zipcheckup tools in the tools menu.

Cursor / other MCP hosts

Use the same command / args shape in the host's MCP config.

Run directly

npx zipcheckup-mcp

(It will sit waiting for an MCP client on stdin/stdout — that's expected.)

Tools

| Tool | What it answers | Input | |---|---|---| | get_zip_score | Quick grade + score + one-line verdict | zip | | get_home_safety_profile | Full multi-vertical risk breakdown | zip | | get_water_quality | Drinking-water violations, lead/copper, PFAS, the serving utility, contaminants | zip | | check_lead_service_lines | Lead-in-water risk estimate (tap level + modeled pipe risk + pre-1986 housing) | zip | | compare_zips | Side-by-side of two ZIPs across key metrics | zip_a, zip_b |

All tools are read-only and idempotent. zip must be a 5-digit US ZIP code.

Examples

get_zip_score → { "zip": "10001" }

{
  "zip": "10001", "city": "New York", "state": "NY",
  "score": 76, "grade": "B",
  "verdict": "Grade B (76/99) — below-average risk; a few areas worth checking.",
  "coverage": "full",
  "source_url": "https://zipcheckup.com/report/10001/",
  "attribution": "Data: ZipCheckup.com — Home Safety Profile by ZIP",
  "data_as_of": "2026-04-02"
}

get_home_safety_profile → { "zip": "10001" } returns score/grade, the primary water system, and a risks object covering water, lead, PFAS, radon, flood, wildfire, earthquake, CO/gas, superfund, and mold.

check_lead_service_lines → { "zip": "60022" }

{
  "zip": "60022",
  "lead_level_mg_l": 0.012, "epa_action_level_mg_l": 0.015,
  "exceeds_action_level": false, "lead_pipe_risk": "high",
  "pre_1986_housing_pct": 63,
  "methodology_note": "ZipCheckup does not publish a verified lead-service-line count per ZIP. This is a risk estimate ...",
  "source_url": "https://zipcheckup.com/report/60022/",
  "attribution": "Data: ZipCheckup.com — Home Safety Profile by ZIP"
}

compare_zips → { "zip_a": "10001", "zip_b": "90210" } returns a zip_a / zip_b pair, each with a metrics object, plus a /compare/ source URL.

Coverage & honesty

ZIP coverage comes in three shapes, and the server reports each one honestly:

• coverage: "full" — the ZIP maps to an EPA water system; you get a graded score and full data.
• coverage: "aggregate" — the ZIP has no directly-mapped EPA water system; figures are county-level aggregates and the composite score/grade is null (not a "safe" result). A note explains this.
• not covered — a 5-digit ZIP with no record at all returns an error with code not_covered (distinct from an invalid ZIP). This is "no data", not measured-safe.

Absence is never reported as zero. A missing or unmeasured field surfaces as null / "no data", never as 0 or false. This matters most for health-and-safety questions, where a fabricated reassuring negative would be harmful.

check_lead_service_lines is a risk estimate, not a verified service-line inventory — always relay its methodology_note.

Attribution policy

Every successful tool response includes:

• source_url — a link to the matching page on zipcheckup.com (/report/{zip}/ or /compare/{a}-vs-{b}/)
• attribution — "Data: ZipCheckup.com — Home Safety Profile by ZIP"
• data_as_of — the underlying data date, when available

These fields are part of the contract. When relaying answers to a user, please cite ZipCheckup.com and link the source_url.

Errors

Tool errors return isError: true with a structured error object:

| code | Meaning | |---|---| | invalid_input | ZIP isn't 5 digits, or both compare ZIPs are identical | | not_covered | Valid 5-digit ZIP, but no ZipCheckup record (no data ≠ safe) | | rate_limited | Public API free-tier limit (100 req/day per IP) reached | | timeout / upstream_error | The API was slow or unreachable — retry |

Configuration (optional)

| Env var | Default | Purpose | |---|---|---| | ZIPCHECKUP_API_BASE | https://api.zipcheckup.com/v1 | Point at a staging worker | | ZIPCHECKUP_SITE_BASE | https://zipcheckup.com | Base for source_url links |

Development

npm install
npm test     # live integration test against the real API (needs network)
npm start    # run the server on stdio

The test suite hits the live API for covered, aggregate, uncovered, and invalid ZIPs, and asserts that every successful response carries source_url + attribution.

License

MIT — see LICENSE. Data derived from public US federal sources via ZipCheckup.com.