validate_iban

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

Annotations already indicate read-only and idempotent behavior. The description adds crucial details: automatic space stripping, output format for valid and malformed inputs, and the limitation that it only validates structure/checksum. This exceeds what structured fields provide.

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 concise (under 200 words) and front-loaded with the core purpose. Every sentence adds necessary information—algorithm, countries, output, limitations—without redundancy.

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?

Given the simple parameter and presence of output schema (implied), the description fully covers validation algorithm, supported countries, input handling, return values, and limitations. No gaps remain for an agent to invoke the tool correctly.

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%, so baseline is 3. The description adds value by explaining that spaces are automatically stripped and providing an example IBAN. This clarifies the parameter format beyond the schema description.

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 clearly states that the tool validates an IBAN using the ISO 13616 MOD-97 algorithm and lists supported countries. It distinguishes itself from sibling validation tools (e.g., VAT, tax ID) by focusing specifically on 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 explicitly lists when to use the tool (SEPA transfers, direct debit mandates, e-commerce checkouts) and implicitly notes when not to use it by stating it does not confirm account existence. This differentiation guides correct selection among sibling validators.

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