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

With no annotations, the description carries the full burden, and it does disclose key traits: the check is offline (no network/lookup), free, and purely a format/check-digit validation that does not confirm registration. It omits what an invalid input returns (error vs. false-like result), which would be valuable given there is no output schema.

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 short sentences with zero filler. The core purpose is front-loaded and the limitation follows immediately.

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 one-parameter validator, the description sets expectations well: it defines exactly what is validated and what is out of scope. The only gap is the return value, since no output schema exists to explain what a pass/fail result looks like.

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 parameter is documented with an example ('Italian partita IVA, e.g. 00743110157'), so the schema already does the work. The description's '11 digits + check digit' reinforces the expected format but adds little beyond 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 names a specific verb and resource ('check of an Italian partita IVA') and scopes it precisely as an 11-digit + check-digit format validation. It distinguishes itself from the lookup sibling by declaring 'Does not confirm registration,' though it never names lookup_italian_pa explicitly.

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?

It gives clear context ('free offline check') and an explicit exclusion boundary ('Does not confirm registration'), which steers the agent away from using it for registration verification. It stops short of naming the alternative tool, so it is not a full 5.

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