Free EU VAT-ID FORMAT check (syntax only, no registry lookup), rate-limited per IP, no API key needed. For a live VIES registry check use the paid validate_vatid tool (5 credits).
| Name | Required | Description | Default |
|---|---|---|---|
| vatId | Yes |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses that it is free, syntax-only (no registry lookup), rate-limited per IP, and requires no API key. While it does not describe the response format or exact rate limits, the disclosed traits are significantly helpful for an AI agent.
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?
The description is two sentences, front-loading the core purpose and adding key context. Every phrase earns its place, with no redundant wording.
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?
For a single-parameter tool with no output schema, the description covers the essential context: purpose, limitations, rate limit, auth-free access, and an alternative. It omits what the return value looks like, but for a validation tool this is often implied. Overall, the description is sufficient for safe selection and invocation.
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 has one parameter (vatId) with min/max lengths but no description. The tool description does not explicitly explain the parameter, though 'EU VAT-ID' in the description clarifies the expected domain. The description adds some context but does not fully compensate for the 0% schema description 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 a specific verb ('check') and resource ('EU VAT-ID format'), with scope: syntax only, no registry lookup. It distinguishes this tool from the paid validate_vatid tool, which performs live VIES checks, ensuring no confusion with sibling tools.
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?
Explicitly states when to use this tool (for format checks) and when to use the alternative (paid validate_vatid for live VIES registry checks). Also notes rate limiting and lack of API key requirement, providing clear context for selection.
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.
Most tools are clearly distinct, but validate_vatid and validate_vatid_format could be confused at a glance, and verify_company overlaps with validate_iban and validate_vatid in scope. However, detailed descriptions and explicit mentions of differences help an agent choose correctly.
All tools follow a consistent verb_noun pattern with lowercase and underscores: screen_sanctions, validate_email, validate_iban, validate_vatid, validate_vatid_format, verify_company. The verb varies but the structure is uniform.
Six tools is a well-scoped number for a validation API covering sanctions, email, IBAN, VAT, and a combined company verification. Each tool serves a clear purpose, and the count feels neither sparse nor bloated.
The set covers core validation areas (sanctions, email, IBAN, VAT, company verification) but intentionally excludes PEP screening and commercial-register checks, as noted in the descriptions. These minor gaps do not prevent core workflows, though they limit full KYC coverage.