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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so 'Read-only' is largely redundant. However, the caveat that 'The note rate is an example, not a quote' is genuine added context an agent must relay, which slightly exceeds the annotation coverage.

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 compact sentences, front-loaded with the core purpose and output scope, followed by the read-only and disclaimer notes. No filler, though the sentence structure is slightly compressed.

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 carries the return-value burden and does so reasonably by specifying year-by-year breakdown vs upfront cost. The two undocumented numeric params (noteRate, termYears) are the main remaining gap, but the required inputs are enumerated.

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 only 40%, but the description's naming of the buydown variants partially maps to the buydownType enum, a value already visible in the schema. It adds little meaning for noteRate, termYears, or loanAmount beyond what the schema states, so it only marginally compensates for the coverage gap.

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?

Specific verb+resource ('Calculate buydown') with explicit output scope: year-by-year P&I and subsidy cost for temporary buydowns vs upfront cost for permanent points. This clearly distinguishes it from siblings like calculate_mortgage_payment and calculate_affordability.

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 when the tool applies by enumerating buydown products (2-1, 1-0, 3-2-1, permanent points), but gives no explicit when/when-not guidance or named alternatives among the many sibling calculators. Usage is inferable from the product list rather than stated.

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