Zip Code Grounding Data

Overview

A US zip code lookup API: get the city and state from a zip code, or list every ZIP code in a city. Zip Codes Lookup works by querying a database of US zip codes and returns the matches as JSON with each ZIP's primary county, with county FIPS codes, time zone, latitude, longitude and ZIP-to-ZIP distance on paid plans.

Live Test Zip Code Grounding Data Source →

The tool

Once your client is connected to the VerveContext server, this appears in its tool list as ZipCodeGroundingData. It is read-only and open-world — it fetches and never mutates anything on your side — so most clients call it without asking you to confirm.

{
  "name": "ZipCodeGroundingData",
  "arguments": {
    "zip": "64082"
  }
}

You do not name the tool yourself; the model picks it. Asking about 64082 in the terms this source covers is enough for it to reach for ZipCodeGroundingData on its own — naming it explicitly also works, and is the way to force the call.

Connecting

One server URL covers every source in the catalog, including this one. Authorization is OAuth: the client opens a browser once, and there is no key to paste into a config file.

{
  "mcpServers": {
    "vervecontext": {
      "url": "https://api.vervecontext.com/v1/mcp"
    }
  }
}

https://api.vervecontext.com/v1/mcp

Per-client setup — Claude, Cursor, VS Code, ChatGPT — is on the MCP setup page.

Arguments

These are the properties on the tool's inputSchema, so a well-behaved client validates them before the call is made. Premium arguments are accepted on every plan but only take effect on plans that include them.

What the model gets back

The result carries a structuredContent object matching the tool's declared outputSchema, so a client reads fields without parsing prose. status is "ok" and error is null on success; a null field means the value was not available for that input, not that the call failed.

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{
  "status": "ok",
  "error": null,
  "data": {
    "zipcode": "64082",
    "state_abbr": "MO",
    "latitude": "38.850243",
    "longitude": "-94.39570",
    "city": "Lees Summit",
    "state": "Missouri",
    "timezone": "America/Chicago",
    "county": "Jackson County",
    "countyFips": "29095",
    "stateFips": "29",
    "counties": [
      {
        "name": "Jackson County",
        "fips": "29095",
        "landShare": 0.9077
      },
      {
        "name": "Cass County",
        "fips": "29037",
        "landShare": 0.0923
      }
    ],
    "distance": {
      "zipcode": "64106",
      "city": "Kansas City",
      "state_abbr": "MO",
      "miles": 19.94,
      "kilometers": 32.09
    }
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Why ground on it

A model can produce something that looks like this answer from its training data, and be confidently out of date or simply wrong. This source returns the current value in a shape you can check, which is the difference between an answer you can cite and one you have to hedge.

Point an evaluation at zipcode: it is the field most worth pinning a claim to, and it is either present and current or absent — never plausibly invented.

Failure modes

Errors come back as tool errors carrying a sentence the model can act on, not a bare status code. Error handling covers the full list.

A call costs 2 credits each time the tool actually runs; a model that reasons about the tool without calling it costs nothing.

Use cases

Checkout Address Autofill

Fill in city and state names automatically when an online shopper types their five-digit postal code during checkout.

Delivery Zone Assignment

Dispatch software queries a target city and state to collect every valid postal code before assigning regional courier routes.

Territory Sales Mapping

When sorting sales leads, CRM systems look up postal codes to group prospects under the correct state and municipal account reps.

Shipping Address Verification

To prevent delivery exceptions, order management systems check customer-entered postal codes against returned state codes before processing fulfillment.

Other ways to use Zip Code Grounding Data

Set up Zip Code Grounding Data on VerveContext, or reach the same source a different way. Your VerveContext account and credits work on all of them — one key, one balance.

Related

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