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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the description does not need to emphasize safety. The description adds value by stating 'Returns the computed IBAN with correct checksum,' which informs the agent of the output format. No contradiction with annotations.

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 two sentences, each carrying essential information. The first sentence lists inputs and action; the second sentence describes output and use case. No unnecessary words, and the most critical 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?

Given the tool's simplicity (calculation from inputs) and the presence of an output schema, the description is complete. It covers what the tool does, what inputs are needed (including optional ones), what it returns, and a practical use case. No missing critical details.

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?

Input schema coverage is 100%, with each parameter already having a clear description. The description adds minimal extra meaning: it notes that branch_code is optional and clarifies the domestic nature of bank_code and account_number. Since the schema does the heavy lifting, the description provides only marginal additional value.

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 the tool's function: 'Calculate a valid IBAN from domestic bank routing details.' It lists the required inputs (country code, bank code, account number) and optional branch code, and specifies the output (IBAN with checksum). This clearly differentiates it from the sibling tool 'iban.banking.validate' which focuses on validation rather than generation.

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 implies usage for payment automation ('Useful for payment automation.') and contextually suggests it is for generating IBANs, not validating them. However, it does not explicitly state when to use this tool versus the sibling 'iban.banking.validate' or mention scenarios where this tool is not appropriate. Slight room for improvement.

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