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

With no annotations provided, the description carries full behavioral disclosure burden. It states the tool compares monthly payments, identifies break-even, and evaluates whether a lower rate costs more overall, but it does not disclose assumptions (e.g., fixed-rate loans, exclusion of taxes/PMI), how closing costs are factored, or the structure of results. This is partial transparency.

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 a single, focused sentence that front-loads the tool name and lists three specific benefits without filler. Each clause conveys distinct, useful information, making it highly concise and well-structured.

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?

This tool has six required parameters, no output schema, and no annotations, yet the description only gives high-level purpose. It fails to mention required inputs, how to interpret break-even, or what calculations are performed. An agent would need to guess parameter meanings and output format, making the description inadequate for correct invocation.

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 0%, and the description adds no meaning to any of the six parameters. It does not explain that currentBalance is the outstanding principal, that rates are percentages, or that closingCosts are essential for the break-even calculation. Parameter names are self-descriptive but not sufficient to understand nuanced inputs like remainingTermMonths versus newTermMonths.

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 uses a specific verb ('find out') and resource ('refinancing your mortgage'), and enumerates concrete outputs: comparing monthly payments, determining break-even, and detecting when a lower rate costs more overall. This clearly distinguishes it from sibling calculators like mortgage_overpayment_calculator (extra payments) and loan_amortization_calculator (repayment schedule).

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 a usage scenario ('Find out if refinancing your mortgage is worth it') but does not explicitly state when to use this tool versus alternatives. It mentions no exclusions, prerequisites, or comparisons to siblings such as mortgage_points_calculator, leaving the agent to infer usage from the name and generic statement.

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