Validate IBAN

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

With zero annotations, the description carries full burden and does add useful non-obvious behaviors: spaces are stripped and letters are case-insensitive. However, it omits other behavioral traits like side-effect-free execution, error behavior on invalid input, or whether validation is local. Adds genuine context but doesn't fully cover the space.

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 efficient sentences: the first states purpose and validation depth; the second covers input normalization edge cases. Zero wasted words, information density is excellent, and the most important information is front-loaded.

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 validation tool with an output schema, this description is nearly complete: it explains the validation logic (length + checksum) and accepted input forms. Annotations are absent, so a note on read-only/side-effect-free semantics would push it to 5, but the scope is fully appropriate for its complexity.

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 0%, so the description must compensate—and it does by explaining that the iban string tolerates spaces (stripped) and case variations. This meaningfully enriches the bare schema definition (string, 4-50 chars). Could go further by noting whether other whitespace (tabs) is stripped, but for one parameter it's well-handled.

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?

Uses a specific verb ('Validates') with a well-defined resource ('International Bank Account Number (IBAN)') and names the exact validation standard (ISO 13616) and checksum algorithm (mod-97). The IBAN domain is self-evidently distinct from sibling card tools, and the technical specificity makes the tool's scope unmistakable.

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 clarifies what 'validates' means by specifying both length checks and checksum verification, giving agents a clear sense of this tool's validation depth. However, it provides no explicit when-to-use vs. alternatives (e.g., no contrast with validate_card_number or note that this is local-only validation).

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