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nordic-data

by io.github.Mnymann
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validate_vat

Read-onlyIdempotent

Call before issuing an invoice, processing a cross-border payment, or storing a counterparty's VAT number. Validate a VAT registration number for any of the 27 EU member states against the official EU VIES service (DK is checked against the national CVR register). Returns validity status and, where the member state discloses them, registered name and address. Use EL for Greece. Not supported: United Kingdom (GB) and Norway (NO) — for a Norwegian company, lookup_company with country 'no' reports vatRegistered from Brønnøysund. HTTP 503 upstream_unavailable means that member state's VIES node is temporarily down; retry later.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
countryYesVIES country code, UPPERCASE. Supports the 27 EU member states. Use EL for Greece (not GR). The United Kingdom (GB) and Norway (NO) are not supported.
vat_numberYesVAT number WITHOUT country prefix — just the digits/characters. Example: for DK29403473, pass '29403473'.

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
nameNoRegistered company name. null when the member state does not disclose trader details via VIES (e.g. DE, ES) — the number can still be valid.
validNoTrue if the source confirms the number is registered and active.
sourceNoValidation source, e.g. 'VIES' or 'CVR' (DK).
addressNoRegistered address. null when not disclosed by the member state.
vatNumberNoFull VAT number including country prefix, e.g. DE143454214.
countryCodeNoCountry code (uppercase).

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed4 schema fields changed
    • changedInput schema / properties / country / description
      Previous value: -"ISO 3166-1 alpha-2 country code, UPPERCASE. Use GB for the United Kingdom (HMRC), not UK. Supports all EU member states plus GB and NO."New value: +"VIES country code, UPPERCASE. Supports the 27 EU member states. Use EL for Greece (not GR). The United Kingdom (GB) and Norway (NO) are not supported."
    • changedInput schema / properties / country / enum
      Previous value: -[
-  "DK",
-  "NO",
-  "SE",
-  "FI",
-  "NL",
-  "BE",
-  "IE",
-  "GB",
-  "FR",
-  "DE",
-  "CZ",
-  "PL",
-  "LV",
-  "EE",
-  "AT",
-  "BG",
-  "CY",
-  "HR",
-  "ES",
-  "IT",
-  "LU",
-  "MT",
-  "PT",
-  "RO",
-  "SI",
-  "SK",
-  "HU",
-  "GR",
-  "LT"
-]New value: +[
+  "AT",
+  "BE",
+  "BG",
+  "CY",
+  "CZ",
+  "DE",
+  "DK",
+  "EE",
+  "EL",
+  "ES",
+  "FI",
+  "FR",
+  "HR",
+  "HU",
+  "IE",
+  "IT",
+  "LT",
+  "LU",
+  "LV",
+  "MT",
+  "NL",
+  "PL",
+  "PT",
+  "RO",
+  "SE",
+  "SI",
+  "SK"
+]
    • changedOutput schema / properties / source / description
      Previous value: -"Either 'VIES' or 'HMRC'."New value: +"Validation source, e.g. 'VIES' or 'CVR' (DK)."
    • changedOutput schema / properties / valid / description
      Previous value: -"True if VIES / HMRC confirms the number is registered and active."New value: +"True if the source confirms the number is registered and active."
  2. Changed11 schema fields changed
    • changedOutput schema / properties / address / description
      Previous value: -"Registered address, if disclosed."New value: +"Registered address. null when not disclosed by the member state."
    • changedOutput schema / properties / address / type
      Previous value: -"string"New value: +[
+  "string",
+  "null"
+]
    • removedOutput schema / properties / checked_at
      Removed value: -{
-  "description": "ISO-8601 timestamp of the validation.",
-  "type": "string"
-}
    • removedOutput schema / properties / country
      Removed value: -{
-  "description": "Country code echoed back (uppercase).",
-  "type": "string"
-}
    • addedOutput schema / properties / countryCode
      Added value: +{
+  "description": "Country code (uppercase).",
+  "type": [
+    "string",
+    "null"
+  ]
+}
    • changedOutput schema / properties / name / description
      Previous value: -"Registered company name, if disclosed by the source."New value: +"Registered company name. null when the member state does not disclose trader details via VIES (e.g. DE, ES) — the number can still be valid."
    • changedOutput schema / properties / name / type
      Previous value: -"string"New value: +[
+  "string",
+  "null"
+]
    • changedOutput schema / properties / source / type
      Previous value: -"string"New value: +[
+  "string",
+  "null"
+]
    • changedOutput schema / properties / valid / type
      Previous value: -"boolean"New value: +[
+  "boolean",
+  "null"
+]
    • addedOutput schema / properties / vatNumber
      Added value: +{
+  "description": "Full VAT number including country prefix, e.g. DE143454214.",
+  "type": [
+    "string",
+    "null"
+  ]
+}
    • removedOutput schema / properties / vat_number
      Removed value: -{
-  "description": "Submitted VAT number (without country prefix).",
-  "type": "string"
-}
  3. First observed

TDQS

A4.6/5.0
Behavior5/5

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

Annotations already provide readOnlyHint, openWorldHint, and idempotentHint, but the description adds valuable context beyond them: the data source (VIES, with DK via CVR), the return fields (validity status, possibly registered name/address), and the meaning of HTTP 503 upstream_unavailable with retry guidance. This enriches the agent's understanding of behavior without contradicting the annotations.

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

Conciseness4/5

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

The description is compact and front-loaded with the most critical usage guidance, followed by purpose, return info, edge cases, and error handling. It is dense but every sentence carries relevant information; a slightly more structured layout could improve scannability, but there is no waste.

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?

For a 2-parameter read-only tool with an output schema, the description covers everything needed to invoke it correctly: when to use it, unsupported cases, alternative tools, special country handling, and error semantics. The output schema covers return values, so the description is contextually complete.

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 fully documents both parameters. The description largely repeats schema facts ('Use EL for Greece', 'VAT number WITHOUT country prefix') rather than adding new semantic meaning. Baseline 3 applies because the schema carries the load adequately.

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?

The description states a specific verb and resource: 'Validate a VAT registration number for any of the 27 EU member states against the official EU VIES service.' It clearly distinguishes itself from sibling tools by explicitly naming lookup_company as the alternative for Norway, so an agent can tell them apart.

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?

The description opens with explicit when-to-use guidance: 'Call before issuing an invoice, processing a cross-border payment, or storing a counterparty's VAT number.' It also states what is not supported (GB, NO) and gives a concrete alternative for Norway, making the selection criteria fully explicit.

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

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