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

Annotated as readOnlyHint=true, and the description adds behavioral context: it is an arithmetic estimate only, not a loan offer or rate quote. This clarifies the tool's limitations beyond the annotation, earning a score above baseline.

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?

Two concise sentences with no wasted words. The core function and key qualifiers (currency-agnostic, optional DTI, non-advice disclaimer) are front-loaded. Every sentence is necessary and informative.

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?

For a 4-parameter tool with no output schema, the description adequately conveys inputs and the nature of outputs (monthly payment, total interest, DTI). It could explicitly list return fields but is still complete enough given the straightforward calculation.

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 100%, so baseline is 3. The description adds that monthly_income enables debt-to-income ratio and that annual_rate accepts decimal or percent, but the schema already includes these details. Overall, description reinforces but adds only modest 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 estimates monthly mortgage payment and total interest, and optionally computes debt-to-income ratio. It uses specific verb phrases and distinguishes itself from siblings, none of which are mortgage calculators.

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 clear context: it is currency-agnostic, informational, and not financial advice. It implies when to use (for estimates) but does not explicitly list when not to use or compare to sibling tools, though siblings are largely unrelated.

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