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

No annotations are provided, so the description carries the transparency burden. It discloses useful behavioral details: 8-character bank codes may resolve to a name, unknown ones return bankName null, test BICs are flagged, and XXX is treated as the primary office. It also warns that a structurally valid BIC may still be unissued, deactivated, or mistyped.

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 front-loaded with a strong purpose statement and each sentence conveys a distinct, useful idea. It is slightly long-winded because it repeats 'checks'/'ISO 9362' and includes payment-file motivation, but it never becomes verbose or irrelevant.

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 validation tool with one parameter and no output schema, the description gives strong context: it explains components, well-known names, test BICs, the directory-lookup caveat, and the possibility of false structural confidence. The only minor gap is that it doesn't describe the exact response shape for an invalid BIC, such as a valid boolean versus thrown errors.

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?

The schema already explains the bic parameter with 100% coverage, so the baseline is 3. The description mostly restates the same length/spacing constraints and adds behavioral context such as location-code 0 semantics. It does not add meaningfully new parameter-specific guidance beyond that.

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 states a specific action ('Checks a SWIFT/BIC against ISO 9362 structure'), names the exact resource, and further explains it splits bank/country/location/branch and may resolve well-known institutions. This clearly differentiates it from the sibling validator tools.

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 clear context for when this tool is relevant: validating BIC structure for payment files, flagging test BICs, and confirming ISO 9362 pattern. It also provides an important when-not guarantee: it is not a SWIFT directory lookup. It does not name alternative sibling tools explicitly, but the exclusion is clear.

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