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

Even though annotations indicate readOnlyHint=false, the description goes further by detailing exact side effects: a never-seen IBAN is recorded as 'pending confirmation' and an alert email is sent to the account holder. It also states the requirement for an API key and that credits are not consumed, providing complete transparency.

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?

The description is a bit long but each sentence carries necessary warnings and operational details, front-loaded with the core purpose. The 'ATTENZIONE' warning effectively highlights the critical state-modification aspect.

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 tool with side effects, API key requirement, and a manual follow-up step, the description is remarkably complete. It covers what the tool does, what changes it makes, what it cannot do (confirmation), and where the human confirmation process happens, leaving no major gaps.

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%, with each parameter already documented. The description adds contextual meaning (IBAN is 'letto su una fattura') but does not explain param relationships (e.g., anyOf requirement) beyond what the schema provides. Baseline of 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?

The description clearly states the tool's function: comparing an IBAN from an invoice against the supplier's history and reporting whether it is confirmed, seen but unconfirmed, or never seen. This distinguishes it from sibling tools like validate_iban (syntax validation) and guardian_supplier_status.

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 phrase 'Il gesto anti-BEC' gives clear context for when to use the tool (invoice payment fraud prevention). It also explicitly states that IBAN confirmation is not exposed to agents, indicating a clear non-goal. However, it does not explicitly name alternative tools or scenarios where another tool would be preferred.

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