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

With no annotations, the description carries the behavioral burden and does disclose useful non-schema behavior: the amortization-based components included in the monthly breakdown and the requirement to surface calculator_url as a clickable markdown link. It does not explicitly state side-effect or permission behavior, but a mortgage calculator is implicitly non-mutating.

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 two tight sentences. The first front-loads what is calculated and the second gives an important presentation instruction with no wasted words.

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 10-parameter calculator with no output schema, the description covers the core computation and an important output field behavior. It could go further in describing the result shape or when to request the amortization schedule, but the schema handles parameter details well.

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 all 10 parameters, including defaults and the down_payment_usd override. The description adds useful context by listing the payment components, but it does not provide parameter-specific semantics beyond what the schema supplies.

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 states a specific calculation: monthly mortgage payment breakdown including principal, interest, property tax, insurance, PMI, and HOA. It is clear what the tool computes, but it does not distinguish itself from nearby siblings such as calculate_loan, calculate_affordability, or calculate_biweekly_mortgage.

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 gives no explicit when-to-use or when-not-to-use guidance, nor does it name alternatives among the many calculator siblings. Usage is only implied by the tool name and the mortgage-specific output.

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