Sales Tax Grounding Data

Overview

Pass a five-digit ZIP code or a two-letter state code to retrieve applicable tax rates. Querying a state returns its base tax rate, while a ZIP code returns the estimated combined rate. Paid plans add granular rate breakdowns covering county, city, and special district jurisdictions.

Live Test Sales Tax Grounding Data Source →

The tool

Once your client is connected to the VerveContext server, this appears in its tool list as SalesTaxGroundingData. 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": "SalesTaxGroundingData",
  "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 SalesTaxGroundingData 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": {
    "state": "CA",
    "zip": 90210,
    "region": "WEST HOLLYWOOD TOURISM IMPROVEMENT DISTRICT",
    "rate": 0.1025,
    "county": 0.0025,
    "city": 0.0075,
    "special": 0.0325
  }
}

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A model can produce something that looks like this answer from its training data, and be confidently out of date or simply wrong.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 state: 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

Online Store Checkout

When a customer enters their shipping ZIP code, e-commerce checkouts apply the matching combined rate to calculate cart totals.

Automated Invoice Generation

B2B billing platforms look up state tax rates to append accurate tax line items to monthly customer invoices.

Point of Sale Calculation

Retail POS systems query store location ZIP codes during setup to store local tax percentages for offline transactions.

Subscription Billing Quotes

SaaS quote generators calculate estimated local taxes before sending multi-state sales proposals to prospective corporate clients.

Other ways to use Sales Tax Grounding Data

Set up Sales Tax 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.

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