# HUD-USPS ZIP Code Crosswalk Resolver

> HUD-USPS ZIP Code Crosswalk Resolver is a paid API for AI agents from 2s.io, paid per call via x402, $0.012/call, status unknown (last checked 2026-09-14).

Resolves a US ZIP code to overlapping census tracts, counties, CBSAs (metro areas), and congressional districts with HUD-USPS allocation ratios by address type

## Facts

- Endpoint: GET https://2s.io/api/geo/zip-resolve
- Price: $0.012/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hud-usps-zip-code-crosswalk-resolver-64cb5497
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_G9Rou47bXRAYHOyfLOmbY

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability hud-usps-zip-code-crosswalk-resolver-64cb5497
```

Example prompt: What census tracts, county, metro area, and congressional district does ZIP code 90210 fall in — and what are the HUD-USPS allocation ratios showing how much of that ZIP is in each geography?

## When to prefer this

Use this endpoint when you have ZIP-coded data and need to join it to datasets keyed by county FIPS, census tract, CBSA, or congressional district — especially when you need proper allocation ratios to handle ZIP codes that span multiple geographies. Prefer this over simple centroid-based lookups when accuracy of split-geography attribution matters.

## Known failure modes

- Invalid or non-existent ZIP code returns an error or empty result
- ZIP codes for PO Boxes or unique ZIP codes (e.g. for large organizations) may have unusual or no crosswalk data
- Recently retired or newly created ZIP codes may not appear in the HUD-USPS dataset
- Missing 'zip' query parameter returns a 400 or validation error

## How this service works

Resolve a US ZIP code to the census tract(s), county, CBSA (metro), and congressional district it covers — each with HUD-USPS allocation ratios (by residential, business, other, and total address counts). A ZIP is a mail-delivery route set, not a polygon, so it spans multiple geographies; the ratios tell you how much of the ZIP falls in each — the canonical join when you have a ZIP but a dataset is keyed by county/tract/district. Source: HUD-USPS ZIP Crosswalk (public domain).

## Output

A list of geographic units (census tracts, counties, CBSAs, congressional districts) that overlap the given ZIP code, each with HUD-USPS allocation ratios broken down by residential, business, other, and total address counts — indicating what fraction of the ZIP falls within each geography.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "queryParams"
   ],
   "properties": {
    "type": {
     "const": "http"
    },
    "method": {
     "const": "GET"
    },
    "queryParams": {
     "required": [
      "zip"
     ],
     "properties": {
      "zip": {
       "type": "string",
       "description": "5-digit US ZIP code."
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hud-usps-zip-code-crosswalk-resolver-64cb5497/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 2s.io](https://www.zero.xyz/host/2s.io/llms.txt)