Calculate mortgage PITI

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

Beyond the annotations (readOnlyHint, idempotentHint), the description adds key behavioral details: it is local-only, no network call, PMI applies automatically when LTV > 80% and 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 two sentences long, front-loading the purpose and then succinctly covering parameter details. Every sentence serves a purpose 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?

Given 10 parameters, no output schema, and rich annotations, the description covers key behaviors (no network call, PITI breakdown, parameter alternatives). It could mention return format but is adequate.

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 only 40% schema description coverage, the description compensates by explaining defaults (down_payment_percent defaults to 20%), conditional PMI behavior, and alternative ways to provide property tax. This adds significant meaning beyond the schema.

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' that returns a 'full PITI breakdown', using specific verbs and distinguishing it from the sibling tool 'homes_calculate_affordability' by focusing on detailed mortgage components.

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 on when to use (local calculation, no network call) and parameter alternatives (e.g., 'Provide either down_payment OR down_payment_percent; defaults to 20%'). It lacks an explicit when-not-to-use statement for other scenarios but is clear enough.

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