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).
/api/geo/zip-resolvePAYMENT-SIGNATURE.The zip resolve API is a pay-per-call geo endpoint built for AI agents and autonomous software. 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).
There is no signup and no API key. An agent (or any HTTP client) hits the endpoint, receives an x402 "402 Payment Required" challenge, signs a sub-cent USDC payment on Base or Solana, and retries — the data comes back on the paid request. That makes it a drop-in zip resolve data source for an agent tool-use loop, an MCP host, or a backend that needs geo data on demand without onboarding to yet another vendor portal.
| Name | Type | Description |
|---|---|---|
ziprequired | string | 5-digit US ZIP code, e.g. 90210. match ^\d{5}$ |
# 1. Probe with no auth → 402 envelope with PaymentRequirements curl -sS 'https://2s.io/api/geo/zip-resolve?zip=12345' # 2. Sign + retry with PAYMENT-SIGNATURE: curl -sS 'https://2s.io/api/geo/zip-resolve?zip=12345' \ -H 'PAYMENT-SIGNATURE: <base64-json-payload>' # Or use the canonical runner (handles probe → sign → retry): # EVM_PRIVATE_KEY=0x... node --env-file=.env.local \ # --experimental-strip-types scripts/x402-pay.ts \ # 'https://2s.io/api/geo/zip-resolve?zip=12345'
import { TwoS } from '@2sio/sdk'
const client = new TwoS({
privateKey: process.env.EVM_PRIVATE_KEY as `0x${string}`,
})
const result = await client.geo.zipResolve({
"zip": "12345"
})
console.log('endpoint:', result.endpoint)
console.log('cost:', result.costUsd, 'USDC')
console.log('tx:', result.settlement?.txHash)
console.log('data:', result.data)import os
from twosio import TwoS
client = TwoS(private_key=os.environ["EVM_PRIVATE_KEY"])
result = client.geo.zip_resolve(zip="12345")
print("endpoint:", result.endpoint)
print("cost:", result.cost_usd, "USDC")
print("tx:", (result.settlement or {}).get("tx_hash"))
print("data:", result.data)// 1. Add @2sio/mcp to your MCP host config (Claude Desktop example below).
// EVM_PRIVATE_KEY funds x402 payments per call.
// claude_desktop_config.json
{
"mcpServers": {
"2sio": {
"command": "npx",
"args": ["-y", "@2sio/mcp"],
"env": { "EVM_PRIVATE_KEY": "0x..." }
}
}
}
// 2. Once the server is running, agents call this tool via standard MCP:
{
"jsonrpc": "2.0",
"id": 1,
"method": "tools/call",
"params": {
"name": "geo.zip-resolve",
"arguments": {
"zip": "12345"
}
}
}| Field | Type | Description |
|---|---|---|
ok | boolean | one of: true |
items | array | |
total | integer | Total matching rows upstream; null when unknown. |
source | object |
{
"ok": true,
"items": [
{
"zip": "example",
"city": "example",
"state": "example",
"tract": [
{
"geoid": "example",
"resRatio": 1,
"busRatio": 1,
"othRatio": 1,
"totRatio": 1
}
],
"county": [
{
"geoid": "example",
"resRatio": 1,
"busRatio": 1,
"othRatio": 1,
"totRatio": 1
}
],
"cbsa": [
{
"geoid": "example",
"resRatio": 1,
"busRatio": 1,
"othRatio": 1,
"totRatio": 1
}
],
"congressionalDistrict": [
{
"geoid": "example",
"resRatio": 1,
"busRatio": 1,
"othRatio": 1,
"totRatio": 1
}
]
}
],
"total": 1,
"source": {
"provider": "example",
"url": "example",
"license": "example"
}
}