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

Annotations already establish read-only, idempotent, non-destructive behavior. The description adds meaningful context beyond those: offline operation, rejection messages name the failed check, structure-only scope, the test-BIC flag, and no wallet/API key requirement. No contradiction with annotations.

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 dense and front-loaded, covering validation scope, caveat, required input, and access details in one compact paragraph. The rhetorical opening adds little technical value, and pricing details add bulk, but nothing is redundant.

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 single-parameter, read-only, idempotent validator with an output schema, this description fully covers what the tool does, its limits, required input, and usage conditions. An agent has everything needed to select and invoke it correctly.

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 the baseline is 3. The description adds valuable format detail (8 or 11 characters, bank/country/location/branch layout) that makes the expected value of 'bic' much more concrete than the schema's 'BIC / SWIFT'.

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 specific verb ('validate'), a clear resource ('a BIC/SWIFT code'), and enumerates concrete checks (length, layout, head-office vs branch, test-BIC flag). This distinguishes it from siblings like iban_check by scoping exactly to ISO 9362.

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?

Clear context is provided: offline validation, structure-only, and an explicit caveat that it 'does not prove the bank is live.' It also states required input and pricing/access model. It does not explicitly name alternative tools for related codes, but the exclusion is clear enough.

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