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

Annotations already declare readOnly, idempotent, non-destructive and openWorld=false, and the description's 'offline' claim is consistent with them. It adds real behavioral context beyond annotations: check-character verification, homocody ('omocodia') handling, century inference, and the different algorithm for 11-digit input.

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, front-loaded with the core purpose and then the two input branches; no filler. It is dense but every clause carries distinct information about validation behavior.

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 annotations covering safety and an output schema covering extraction results, the description only needs to explain validation behavior, which it does for both entity types. Its remaining gaps are how invalid input is reported (error vs. result field) and when to prefer the sibling partita IVA tools.

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?

Only one parameter, and schema description coverage is 100% (it already states 16 characters or 11 digits with an example). The description restates the same format split per entity type but adds no syntax or edge-case detail beyond the schema, so baseline 3 is appropriate.

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+resource ('Validazione offline di un codice fiscale italiano') and spells out both branches: 16-character natural persons and 11-digit legal persons. It does not explicitly distinguish itself from the sibling valida_partita_iva, even though it claims to apply the VAT check for 11-digit input, leaving overlap unclear.

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 implies when the tool applies (validating an Italian tax code, per length) but gives no explicit when-to-use/when-not guidance and never names alternatives. The overlap with valida_partita_iva/verifica_partita_iva for the 11-digit path is left for the agent to resolve.

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