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

The description reinforces the existing annotations by stating it does not access external data or create/modify/delete records. It adds the 'pure calculation' framing and loan type scope, but no additional behavioral details like precision, rounding, or authentication requirements, so it adds only modest value beyond 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 compact and front-loaded with the core action in the first sentence. The second sentence adds important context about side-effects and scope without unnecessary detail. Every sentence earns its place and there is no fluff.

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?

The description is complete for a pure calculation tool: it states the purpose, applicable loan types, and the absence of side effects or external data access. The output schema covers return values. However, it does not explicitly exclude mortgages despite a dedicated sibling tool, and it does not clarify the standard amortization model, leaving minor ambiguity.

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 has 100% description coverage for all three parameters, which already define units and constraints. The tool description rephrases them as 'principal, interest rate, and term' but adds no extra semantic detail beyond what the schema provides, so it meets the baseline 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 states the verb 'calculates' and resource 'installment loan', and lists concrete outputs (monthly payment, total interest, total cost). It scopes to user-supplied principal, interest rate, and term, differentiating from sibling comparison tools by emphasizing it is a pure calculation.

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 states it performs a pure calculation without external data, implying when to use it versus comparison tools. It lists applicable loan types, providing clear context. However, it does not explicitly reference alternatives like calculate_mortgage_payment or state when not to use it.

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