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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds substantive behavioral context beyond that by naming the actual validations performed (8/11-char structure, ISO country, test-BIC flag) and the cross-country fraud signal. It stops short of describing failure behavior or return shape.

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 tightly packed sentences, front-loaded with what is validated and followed by the optional cross-check. Every clause carries information; nothing is padding.

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 no output schema, the description carries the burden of explaining what the caller gets back, and it does not — an agent cannot tell whether this returns a boolean, a structured check breakdown, or throws on invalid input. The input side is fully covered, but the result side is a real gap.

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%, so the baseline is 3; the description earns above it by explaining the purpose of the optional iban parameter (country match as a fraud/typo signal), which adds rationale the schema's terse 'cross-check country' does not convey.

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 precise verb (validate) plus the resource (BIC/SWIFT code) and even enumerates the checks performed: structure, ISO country, test-BIC flag. Against siblings like validate_iban and validate_ein the resource boundary is unmistakable without opening any schema.

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 gives conditional guidance for the optional parameter ('Pass the IBAN too and it checks...'), which is genuinely useful, but it never states when an agent should reach for this tool versus an alternative or what workflow it fits (e.g. pre-payment verification). Usage is implied rather than spelled out.

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