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

Annotations already declare readOnlyHint and openWorldHint, and an output schema exists, so the bar is lower. The description still adds real value by disclosing the 1-credit cost and the precise validation dimensions performed (length, structure, check digits), which the annotations do not cover. It omits any note on rate limits or data freshness for the community report.

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 tightly packed questions plus a cost note in one paragraph, with the core capability front-loaded. The interrogative framing is slightly unusual but efficient; no sentence is 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?

With an output schema handling return values and annotations covering safety and open-world behavior, the description covers what remains: validation scope, bank resolution, community signal, the country-mismatch use case, and cost. Nothing an agent needs to call it correctly is missing.

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%, so baseline would be 3. The description goes beyond the schema by explaining the purpose of claimed_country — comparing it against the IBAN to surface a mismatch — which the schema only describes as 'ISO 3166-1 alpha-2 country the payee claims.' That added intent justifies a 4.

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 resource (IBAN) and enumerates exactly what is returned: validity across country length/structure and check digits, bank name and BIC, and community report status. That is far more specific than the sibling lookup_* tools' bare resource names, so an agent can separate it from lookup_wallet or lookup_payment_handle immediately.

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 a concrete conditional: pass the claimed country specifically to catch a mismatch between what the payee says and what the IBAN encodes. It also states the cost (1 credit), which shapes invocation decisions. It stops short of naming an alternative tool or an explicit when-not-to-use case.

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