vat_mod97_checkStructural VAT check (BE mod-97 family).
| Name | Required | Description | Default |
|---|---|---|---|
| vat_number | Yes | EU VAT id; BE mod-97 checksum (BE prefix optional). |
| Name | Required | Description | Default |
|---|---|---|---|
| tool | No | ||
| scope | No | ||
| valid | Yes | ||
| reason | Yes | ||
| country | No | ||
| normalized | No |
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already indicate read-only/idempotent behavior; the description adds the key behavioral trait that this is a structural (algorithm-based) check, not a registry query. It does not discuss output behavior or edge cases, but output schema exists and safety annotations cover side effects.
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?
Single sentence with precise scoping: 'Structural VAT check (BE mod-97 family)' is front-loaded and contains no filler. Adequately sized for the tool's minimal surface.
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 one-parameter, read-only validation tool with an output schema and rich annotations, the description covers the essential nature of the check. It could strengthen completeness by explicitly noting that the tool only validates structure/checksum and does not check VAT registration status, but that is largely implied by 'structural.'
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?
Schema coverage is 100%, and the schema already documents that vat_number is an EU VAT ID with BE mod-97 checksum and optional BE prefix. The description adds no additional parameter semantics beyond restating the structural nature.
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 identifies a specific resource (VAT) and scope (BE mod-97 family), which distinguishes it from sibling checkers like iban_check or luhn_check. However, 'structural check' is slightly vague and could be interpreted as any VAT validation without explicitly saying it validates Belgian VAT numbers.
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?
No statement about when to use this tool versus alternatives, and no mention that this is only a format/checksum check rather than a registration/status check. Usage must be inferred from the tool name and title.
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.
Each tool targets a distinct identifier type or data source: every checksum validation is for a specific standard (IBAN, LEI, VAT, etc.), and the on-chain and rental tools are clearly separate domains. There is no ambiguity between tools; even similar-sounding checks like 'luhn_check' and 'ean13_check' are distinct algorithms with explicit descriptions.
Most validation tools follow a 'X_check' pattern (iban_check, swift_bic_check, ein_format_check), but others deviate: 'company_number_format' uses a noun_noun structure, 'block_info' is noun_noun, and 'batch_validate' and 'context_distill' use verbs. While the pattern is not uniform, the names are readable and the convention is understandable, just not fully consistent.
With 28 tools, this server exceeds the typical 3-15 well-scoped range and even the 16-25 heavy range. The server covers multiple unrelated domains (identifier validation, blockchain queries, rental fraud, text processing), which inflates the count. While each tool is individually justified, the overall surface feels overly broad for a single MCP server.
For each sub-domain, coverage is strong: identifier validation includes a wide range of international standards, on-chain queries cover balances, activity, and settlement history, and rental tools provide risk, verdict, and deposit guard. Minor gaps exist (e.g., no country-specific tax IDs beyond what's listed, no transaction history for arbitrary tokens), but the visible coverage is comprehensive for the stated purposes.