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

Annotations already declare readOnly, idempotent and non-open-world, so the safety profile is covered. The description adds genuinely useful non-obvious context: the check is structural only and a passing code does not mean the code was issued. It does not say whether a name/surname mismatch fails the whole check or is reported separately.

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?

Front-loaded with the action and the checklist of layers, followed by the important scope caveat. The single long sentence with an embedded parenthetical is dense but there is no 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?

There is no output schema, and the description leaves the result shape ambiguous: 'layer by layer' implies a per-layer breakdown while 'it says whether the code is written correctly' implies a single verdict. For a diagnostic validation tool, stating whether failures are reported per layer would complete the picture.

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 parameter descriptions already state that name maps to characters 4-6 and surname to characters 1-3. The description's mention of 'surname and name letters' restates that, adding only the notion that these are an optional extra layer, not actual syntax or behavior.

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 and resource (check a codice fiscale is well formed) and enumerates exactly what layers are validated: format, check character, birth date, place code valid on that date, and optional name/surname letters. The explicit negative scope ('not whether the Agenzia delle Entrate has assigned it') separates it from both the encode/decode siblings and any authoritative registry lookup.

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?

Clear that this is a syntactic/semantic validation rather than a registration check, and 'optionally the surname and name letters' tells the agent when the two optional parameters come into play. It stops short of naming compute_codice_fiscale or decode_codice_fiscale as the alternatives when the agent instead wants to generate or extract fields.

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