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

Annotations cover read-only and closed-world hints, yet the description still adds real value: rate limits per key tier, data provenance (synthetic but checksum-valid, real bank codes), and a safety boundary against payment use. It stops short of saying calls are non-idempotent/randomized, which the idempotentHint=false annotation implies but the text never confirms.

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?

Four dense sentences that front-load the capability and then layer scope, limits, and the safety caveat. Every sentence carries distinct information; nothing repeats the name or the schema.

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?

This is a simple 3-parameter generator with no output schema, and the description covers provenance, limits, and intended use. The one remaining gap is that it doesn't say what is returned (a list of IBAN strings of length quantity), which an agent must infer.

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 67% — country and bank are documented there, but quantity has no description. The description compensates for bank ('Name a bank to get IBANs of that bank') and explains the daily cap that constrains quantity, though it never clarifies whether quantity caps at 100 or at the key-tier limit.

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 and resource ('Generate synthetic, checksum-valid test IBANs for a country') plus scope details like 119 countries and real bank codes. It doesn't differentiate itself from the sibling tools (bank_test_ibans, calculate_iban, validate_ibans), so an agent must infer which generator to pick.

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?

Gives concrete usage context: quotas without an API key (10/day), and that naming a bank yields that bank's IBANs with free samples or unlimited with a paid key. It also gives an exclusion ('Test data only, never for payments') but never names a sibling tool as the alternative for validation/calculation tasks.

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