Free VIES VAT lookup. Returns VAT validity plus name/address when the member state discloses them; some countries such as ES/DE may return only validity.
| Name | Required | Description | Default |
|---|---|---|---|
| vat | Yes | EU VAT number including ISO-2 country prefix, e.g. "NL123456789B01". |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations declare readOnlyHint=true and openWorldHint=true, and the description adds valuable behavioral context that some countries (ES/DE) may only return validity, not name/address. This goes beyond the annotation hints.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two short sentences immediately convey purpose and a key caveat. Every word earns its place, with no redundancy or filler.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With no output schema, the description explains what is returned (validity, optional name/address) and notes country-specific limitations. It does not detail the exact response structure, but this is sufficient for a simple read-only lookup tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The schema already fully documents the single 'vat' parameter with a format example. The description adds no additional parameter semantics, so the baseline of 3 is appropriate given high schema coverage.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states this is a VAT lookup tool for EU VAT numbers, and it returns validity plus available company details. It distinguishes from sibling tools by focusing specifically on VAT-based lookup.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description does not explicitly state when to use this tool versus get_company or search_company. It implies a use case (VAT lookup) but provides no guidance on alternatives or exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.
The three tools have clearly distinct primary functions: get_company by national ID, lookup_company_by_vat by VAT number, and search_company by name. Some overlap exists on VAT lookups for certain countries, but descriptions clarify the differences.
All tool names follow a consistent verb_noun pattern: get_company, lookup_company_by_vat, search_company. The verbs are semantically appropriate for retrieval operations, and the casing is uniform.
Three tools is on the smaller side, but it is appropriate for a specialized registry lookup server. Each tool covers a distinct query method, so none feels superfluous or redundant.
The server covers the core lookup operations by ID, VAT, and name for supported European registries. Minor gaps exist, such as no separate LEI-specific lookup or batch operations, but the described surface addresses the primary use cases.