Calculate mortgage PITI

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

Annotations indicate readOnlyHint and idempotentHint true, confirming no side effects. The description adds beyond these by stating it is local-only (no network call) and explaining PMI auto-application when LTV > 80% if pmi_rate is provided. No contradiction with 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?

The description is a single paragraph of three sentences. The first sentence establishes the overall purpose, and the remaining sentences provide key parameter semantics. Every sentence adds value, with no extraneous content.

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?

Given 10 parameters, 2 required, and no output schema, the description covers the main functionality, defaults, and parameter relationships. It misses mentioning that loan_term_years defaults to 30 (though schema states that) and could detail the exact output fields, but the core information is present.

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%, so the description must compensate. It does so effectively: explains mutual exclusivity of down_payment and down_payment_percent with default 20%, property tax alternatives, and PMI condition. This adds critical meaning beyond the schema's minimal descriptions.

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 is a local-only mortgage payment calculator returning a full PITI breakdown and total interest. The verb 'calculate' and resource 'mortgage PITI' are specific. None of the sibling tools perform this exact function, so it is well-distinguished.

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 explicit guidance: it is local-only (no network call), and specifies that down_payment or down_payment_percent must be provided (with default 20%), and property tax can be given as annual or rate. It implicitly advises when to use this tool (for mortgage calculations) and clarifies parameter alternatives, though it does not explicitly state when not to use.

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