Validate IBAN

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

No annotations are provided, so the description carries the full burden. It states the tool is a validation/read operation ('Checks whether') which is a non-destructive check. However, it doesn't disclose what the return value looks like (boolean? result object?), error behaviors for malformed input, or any edge-case behavior. It's adequate but not rich.

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 efficient sentence communicates the full purpose: what is checked (structural validity) and the specific algorithm (ISO 7064 mod-97 checksum). Zero wasted words, no redundancy with the schema. The example in the schema complements this nicely.

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?

The tool has minimal complexity (1 param) and 100% schema coverage, so the description is reasonably complete. However, with no annotations and no output schema, the description doesn't explain return semantics — whether it returns a boolean, a status object with error messages, or whether it throws on invalid input. For a validation tool, return-format expectations matter significantly to an agent.

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% — the schema already documents the single iban parameter with a concrete example ('GB29NWBK60161331926819'). The description adds that the IBAN must be validated for structural validity and mod-97 checksum, which reinforces the parameter's semantic usage. At 100% schema coverage, baseline 3 is appropriate and the description meets it.

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 uses a specific verb+resource ('Checks whether a string is a structurally valid IBAN') and clearly specifies what the tool verifies: structural validity AND the ISO 7064 mod-97 checksum. It distinguishes from siblings, which all deal with MT/PACS message conversions/formats, whereas this handles IBAN validation.

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 to use it (to validate an IBAN), which is reasonably clear given the domain context. However, it doesn't explicitly state when NOT to use it or name alternatives, and there's no guidance on what the function returns beyond stating it performs a check. No exclusions or alternative tool references are provided.

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