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

Annotations already cover the safety profile (readOnly, idempotent, closed-world). The description adds real value beyond them by naming the validation algorithm (ISO 13616 mod-97 + country length) and disclosing that bank identification only applies to Swedish IBANs, setting correct expectations. It stops short of describing the return shape or failure behavior.

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?

A single front-loaded sentence that names the action, the standard, and the conditional bank feature with zero wasted words.

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?

There is no output schema, so the description should ideally indicate what a validation call returns (e.g., valid/invalid plus bank details for Swedish IBANs). It hints at bank identification but leaves the return shape unspecified, a notable gap for a validator.

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%, so the single 'value' parameter and its spaces-allowed tolerance are already fully documented. The description adds nothing parameter-specific beyond the baseline.

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 resource (IBAN), plus a secondary capability (bank identification for Swedish IBANs). This clearly distinguishes it from siblings like validate_ocr, validate_bankgiro, and validate_personnummer, which validate entirely different identifiers.

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 scope ('any IBAN' vs Swedish-only bank lookup) implies when to use it, but there is no explicit when-to-use guidance or mention of alternatives such as swedish_account_to_iban, which also deals with IBANs. Usage is inferred rather than stated.

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