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

No annotations are provided, so the description carries the full behavioral burden. It states the two outputs but discloses none of the underlying assumptions an agent would need: fixed-rate amortization, whether the rate is nominal APR, rounding behavior, or currency.

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?

A single front-loaded sentence with zero waste. It is appropriately terse, though the terseness is partly a symptom of missing content rather than disciplined economy.

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?

With no output schema, the description usefully names the return values (monthly payment, total interest), which is the minimum an agent needs. It stops short of explaining the calculation assumptions or confirming the output shape, which a no-annotation, no-output-schema tool would benefit from.

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 description coverage is 100%, so the schema already documents principal, rate, and years, including that the rate is annual. The description adds no parameter-level detail (e.g., that rate is a percentage rather than a decimal) beyond what the schema provides.

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 ('Calculate') and resource ('mortgage payments'), and names the two outputs (monthly payment, total interest). However, it does not distinguish itself from the sibling 'loan_calculator' or 'compound_interest', which likely overlap in function.

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?

No guidance on when to use this versus the sibling loan_calculator or compound_interest tools, and no mention of exclusions (e.g., that it ignores taxes, insurance, or PMI). The agent is left to infer the mortgage-specific use case from the name alone.

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