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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so safety and determinism are covered. The description's contribution is the return-content profile (BIC, domestic code, sample IBANs, bank page, Bank Target Pack link, 250-IBAN cap), which is genuinely useful given there is no output schema, but it says nothing about failure behavior when a bank is not found or about licensing/validity caveats of 'test' IBANs.

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?

One sentence, no padding, but it is a headless noun phrase with the actual action buried and the 250-IBAN limit appearing mid-clause. It is compact yet not front-loaded on what the tool does.

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 only two fully documented parameters, no output schema and clean read-only annotations, the description's enumeration of returned fields is the main missing piece and it supplies it. What remains thin is how a lookup miss behaves, but overall an agent has enough to call this 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 description coverage is 100%: 'bank' already documents that it accepts a name, BIC or domestic bank code, and 'country' accepts a name or ISO code. The description merely echoes those accepted forms, adding no extra syntax or edge-case guidance beyond the schema, so the baseline 3 applies.

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 is a noun phrase describing the payload ("A bank's BIC, domestic bank code and free sample test IBANs...") rather than stating a verb+resource action. An agent can infer this is a per-bank lookup of test IBANs, and that distinguishes it loosely from generate_test_ibans, but the purpose must be reconstructed from the return-value list.

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?

There is no guidance on when to use this versus generate_test_ibans, calculate_iban, or validate_ibans, and no stated prerequisites (e.g., that a known bank and country are required). The only implicit cue is the phrase "for one bank".

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