VAT Check (EU VIES + UK)

check_vat

Verify an EU supplier's or customer's VAT number before invoicing or paying. Checks it live against the European Commission's VIES service (EU-27 and XI Northern Ireland): valid or invalid, plus the registered name and address where the member state publishes them. UK (GB) numbers are not checked on this deployment. Malformed numbers are rejected free, before payment. Use when applying the reverse charge or onboarding a B2B counterparty in the EU. $0.02 per call, USDC on Base (x402).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "vat": "<vat>"
    },
    "name": "check_vat"
  }
}

Input Schema

Name	Required	Description
`vat`	Yes	VAT number with country prefix, e.g. DK34223858, IE6388047V, GB123456789
`proof`	No	Include VIES consultation number (higher price, when enabled)
`payment_signature`	No	x402 v2 PAYMENT-SIGNATURE header value. Omit to receive payment requirements.

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 16, 2026

TDQS

A4.5/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden and covers a lot: live vs. cached checking, geographic coverage limits, the shape of the result (valid/invalid plus name and address where published), the failure mode for malformed input (rejected free), and the cost model ($0.02 per call, USDC on Base, x402). It stops short of operational behavior an agent would want — VIES downtime/timeout handling, retry semantics, or rate limits — which keeps it from a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Roughly six short sentences, each carrying distinct information: purpose, mechanism, coverage boundary, error handling, use case, and cost. Front-loaded with the core action and free of filler or repetition of the tool name.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, but the description compensates by describing what a result contains (valid/invalid plus registered name and address where published) and what a malformed submission yields. Coverage, cost, and the intended decision context are all present, leaving no material gap for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents all three parameters, including the country-prefix format examples and the 'proof' consultation-number flag. The description adds only indirect parameter meaning (GB numbers unverifiable, malformed input rejected pre-payment); the baseline 3 applies when the schema does the heavy lifting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (verify) and resource (EU supplier/customer VAT number) and pins the data source: live check against the European Commission's VIES service. The scope is bounded precisely to EU-27 plus XI Northern Ireland, with GB explicitly excluded, so an agent knows exactly what this tool will and will not answer.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly names the triggering situations ('applying the reverse charge or onboarding a B2B counterparty in the EU') and the workflow position ('before invoicing or paying'). It also names a negative case — UK GB numbers are not checked on this deployment — which is exactly the kind of exclusion that prevents misfires.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All VAT Check (EU VIES + UK) tools Inspect

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