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

No annotations are provided, so the description carries the full behavioral burden. It discloses a material trait the schema cannot: a $0.005 USDC charge on Base via x402. It does not state what happens for an unknown codice fiscale, whether results are cached, or any rate limits, leaving real gaps for a paid network call.

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?

Three sentences, zero padding: the lookup action leads, the usage conditions follow, and the cost is placed last. Every sentence earns its place.

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 and no annotations, the description does well to say what the agent gets back (existence confirmation and PEC addresses) and to warn about the payment mechanism. Minor omissions around error/not-found behavior keep it from a 5.

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 description coverage is 100% and there is only one required parameter, so the schema already documents the format and example. The description restates '11-digit codice fiscale' without adding syntax, validation, or edge-case meaning beyond the schema; baseline 3 applies.

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?

States a specific verb (look up) and resource (Italian public administration / public-service operator) and names the authoritative source (IndicePA, AgID) plus the lookup key (11-digit codice fiscale). It does not distinguish itself from the sibling check_partita_iva_format, which handles a different identifier, so it falls short of a 5.

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?

Gives three concrete triggering scenarios: verifying a public-sector counterparty, retrieving official PEC addresses, and confirming existence before e-invoicing. There is no explicit when-not guidance or named alternative, but the usage context is clear enough to route correctly.

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