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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, yet the description adds genuinely new behavioral context: explicit PII restrictions (no name, email, phone, SSN, street address) and the caveat that rates are illustrative, not quotes. It stops short of describing pagination or output shape, but the PII and disclaimer details are real value beyond the 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?

Three tightly packed sentences with zero filler, and the core purpose (PITI for a Hawaii purchase) is front-loaded ahead of the compliance caveats.

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 14-parameter, output-schema-less calculator, the description conveys what is computed and what data must not be supplied, supplemented by a rich schema. It could mention the shape of the returned estimate, but coverage is otherwise strong.

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 86%, so the schema already documents nearly every parameter (defaults, ranges, PITI components, PMI vs MIP vs funding fee branching). The description reinforces the PITI component set but adds no syntax or format detail the schema lacks; baseline 3 is appropriate.

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?

States a specific verb (Estimate) and a precisely scoped resource (PITI for a Hawaii purchase) and enumerates the components it covers: principal/interest, property tax, insurance, HOA, and PMI/MIP/VA funding fee. This clearly distinguishes it from siblings like compare_loans, calculate_buydown, or 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?

Provides guardrails ('Read-only', no PII fields, rates are examples not quotes) which imply a planning/estimation context, but never states when to choose this tool over calculate_buydown, compare_loans, or rent_vs_buy. Usage is implied rather than routed.

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