Validate IBAN

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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true. Description adds that no data is stored and validation is in-memory, and clarifies error handling: returns valid:false with reason instead of throwing. No contradiction.

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?

The description is efficient: first sentence states purpose, second explains checks, third describes output, fourth provides usage guidance. No useless sentences, 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?

With one parameter, high schema coverage, and no output schema, the description fully covers return fields, error behavior, and data handling. Complete for the tool's 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 coverage is 100% and describes case-insensitivity and space tolerance well. Description does not add extra meaning beyond confirming the parameter is an IBAN. Baseline 3 is appropriate.

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 specifies a clear verb+resource: 'Validate a single IBAN against official ISO 13616 structure.' It distinguishes from sibling tools like validate_bulk_ibans and extract_ibans_from_text, which are mentioned explicitly.

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 provides explicit when-to-use ('Use this when you have one account number to verify'), when-not-to-use ('For many IBANs prefer validate_bulk_ibans'), and alternatives ('to pull IBANs out of prose use extract_ibans_from_text').

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