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

With no annotations present, the description carries the burden and does disclose the key behavioral trait an agent must know before calling: it is a paid x402 call costing $0.005 USDC (or 0.005 EURC) on Base. It does not mention rate limits, error behavior for unknown codice fiscale, or latency.

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 sentences, front-loaded with the verb and resource, then the use cases, then the payment terms. No redundant restatement of the schema 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?

For a single-parameter lookup with no annotations and no output schema, the description covers source, identity, use cases, and the payment gate. It leaves the return payload (legal name, address, PEC list) implicit, so an agent must infer what comes back, which is a minor gap given there is no output schema.

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 single `cf` parameter is fully described with an 11-digit format and an example, so the description need not restate it. The description confirms the 11-digit identifier but adds no syntax, validation, or fallback guidance 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), resource (Italian public administration / public-service operator), identifier (11-digit codice fiscale) and authoritative source (IndicePA, AgID). It does not explicitly contrast with the sibling check_partita_iva_format, but the codice fiscale vs. partita IVA distinction is implicit in the phrasing.

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 when-to-use scenarios: verifying a public-sector counterparty, retrieving official PEC addresses, and confirming existence before e-invoicing. It stops short of naming when not to use it or pointing to the sibling for format-only checks.

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