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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the 'Read-only' line in the description is largely redundant. The description does add two non-schema behavioral facts: the 0.35% Honolulu property-tax default applied unless overridden, and the explicit limit that this is not a forecast — genuinely useful context beyond the 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?

Three short sentences with the core computation front-loaded, followed by the default assumption and the negative scope. Every clause carries information; nothing is padding.

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?

No output schema exists, so the description should signal what the comparison returns (e.g., net difference, break-even year), and it does not. Combined with 18 mostly undocumented parameters and a low schema coverage rate, the definition is under-specified for a computation of this complexity.

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?

With 18 parameters and only 28% schema description coverage, the description must carry weight, yet it only mentions one parameter implicitly (the 0.35% tax rate default). Critical inputs such as loanType, vaFirstUse, vaDisabilityExempt, creditScore, downPaymentUnit, and sellingCostPercent receive no interpretive guidance, leaving most of the parameter surface undocumented.

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 and comparison ('Compare cumulative rent with the net cost of buying over a holding period') and names the dimensions compared, which cleanly distinguishes it from mortgage-payment, affordability, and buydown siblings. The closing 'Not a price or rent forecast' sharpens the tool's remit further.

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 the scenario (choosing between renting and buying) and notes a Honolulu tax default, but gives no explicit when-to-use guidance or routing versus siblings like calculate_affordability or compare_loans. The exclusion of forecasting is useful but is a scope boundary, not a usage rule.

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