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

Annotations already mark the tool as readOnly, idempotent, and non-destructive. The description adds crucial behavioral context: external VIES I/O, honest degradation to 'attenzione' when VIES is down or budget exhausted, the never-false-ok guarantee, free/no-login status, and the non-substitution warning. This richly complements the annotation hints without contradiction.

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 compact yet information-dense, covering purpose, checks, return verdict, external dependency, degradation behavior, cost, access, and a critical caveat in a few sentences. Every sentence earns its place with no fluff or repetition.

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?

Given no output schema, the description clearly states what the tool returns (verdict ok/attenzione/alto_rischio + red flags) and covers failure modes, limitations, and placement among alternatives. It is complete for a tool of this complexity—an agent knows how it behaves, when to use it, and what to expect.

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 input schema covers each parameter with descriptions (100% coverage), so baseline is 3. The tool description adds extra semantic context about verification logic, such as IBAN MOD-97 and ABI checks, VIES live name matching, and expected_country defaulting to IT. It does not exhaustively tie every parameter to its checks, but it meaningfully enriches the schema.

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 states a specific action: 'Verifica anti-frode di un beneficiario PRIMA di pagare una fattura', explicitly distinguishing it from the sibling validation tools by targeting BEC/IBAN-change fraud. It clearly names the resource (beneficiary) and the timing (before payment), going well beyond a generic verb.

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 clearly specifies when to use the tool ('PRIMA di pagare una fattura'), contrasts it with other tools ('A differenza degli altri strumenti fa I/O esterno (VIES)'), and explicitly states what it does NOT replace (out-of-band verification via phone). This gives an agent practical decision guidance.

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