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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering the tool's safe, non-mutating nature. The description adds minimal behavioral context by indicating the payment is monthly and based on a balance, but it does not explain the annual-to-monthly rate conversion or any edge cases. No contradictions 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 a single, concise sentence with no wasted words. It front-loads the core concept and is appropriately sized for a simple calculator tool.

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—two well-documented parameters, strong annotations, and an output schema—the description conveys the essential function. Minor gaps include lacking an explicit verb and not differentiating from sibling tools, but the schema and annotations compensate for most missing context.

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?

The schema provides full descriptions for both parameters ('Outstanding balance' and 'Annual rate in percent') with 100% coverage, so the schema already handles parameter semantics. The description adds no additional parameter context, warranting the baseline score of 3.

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 identifies the tool as computing an interest-only monthly payment on a balance, distinguishing it from related tools like amortization or annuity-payment. However, it uses a noun phrase rather than an explicit verb like 'calculates,' which would make the action more precise.

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 no guidance on when to use this tool versus alternatives. It does not mention any exclusions or reference sibling tools such as amortization or loan-payoff, leaving the agent to infer usage solely from the name.

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