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

No annotations are provided, so the description carries the full behavioral burden. It helpfully lists the validation layers applied (checksum, structure, BBAN, SEPA, formatting), but never states that the operation is non-mutating, whether it performs network/lookup calls for SEPA reachability, or what the result looks like. It adds real value over a bare name but leaves gaps for a no-annotation tool.

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 tight sentences: the core IBAN validation with its checks leads, the optional BIC path follows. No filler or repetition; every clause earns its place.

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 read-only validator with no output schema and no annotations, the description covers what is checked but not what is returned (e.g., validity flag, parsed components, error reasons) or whether SEPA reachability requires external lookups. Adequate for invocation, but incomplete for interpreting results.

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%, with both parameters fully documented (including the 8-11 char BIC range and space tolerance on IBAN). The description reinforces the optional BIC behavior but adds no format or syntax detail 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?

States a specific verb (validate) and a precise resource (IBAN, ISO 13616), and enumerates the exact checks performed (MOD-97-10, country structure, BBAN parsing, SEPA reachability, formatting). The resource is unambiguous relative to disjoint siblings like validate_lei, validate_vat, and validate_iso6346_container.

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 implies when this tool is relevant (any time an IBAN/BIC must be checked) but never states when to prefer it over alternatives or any exclusions. Because siblings operate on entirely different identifiers, routing ambiguity is low, so 3 ('implied usage') is appropriate rather than a penalty.

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