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

Annotations already declare readOnly, idempotent, non-destructive, closed-world. Description adds the multiplier rules (2.5x/3x/3.5x) and the input-mode logic, which is useful behavioral context beyond annotations, but nothing about output format or rounding.

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?

One dense sentence front-loads the three computation modes, followed by a compact input-format instruction. No waste.

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 2-param read-only calculator with no output schema, the description covers input semantics and expected computations well. It doesn't state output shape or default multiplier, a minor gap.

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 covers monthly_income (gross monthly) but monthly_rent has no description and no params are required. The description compensates by specifying monthly figures and mapping which parameter drives which output mode, going 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?

States specific computations: income needed from rent at 2.5x/3x/3.5x, max rent from income at 3x, and ratio when both given. Distinguishes scope through three input modes, clearly different from siblings like rent_affordability or debt_to_income.

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?

Implicit usage is clear: supply rent to get required income, income to get max rent, both to get ratio. Instructs 'Pass monthly figures'. No explicit when-not or alternative naming, but modes are self-routing.

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