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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description adds the time-window semantics (move-in date through month end) but says nothing about rounding, currency, or whether the result is a bare number, which would be genuinely useful context for a calculator.

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?

A single front-loaded sentence that defines the quantity and its time boundary with no filler. Every clause earns its place.

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 small pure-calculation tool with complete safety annotations and no output schema, the definition covers the essential scope. Its only shortfall is not stating that the return is a numeric rent amount, which the phrase 'rent owed' largely implies.

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 67%; the most semantically complex parameter (method, with its three formulas) is already fully documented in the schema. The description only faintly reinforces move_in_date by describing the partial-month window and adds nothing about monthly_rent, so 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 computed quantity (rent owed) and its exact scope (move-in date through the end of that month), which neatly distinguishes it from ratio-style siblings like rent_to_income and rent_affordability. No sibling is named or explicitly contrasted, so it stops short of a 5.

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 phrase 'partial first month' implicitly tells the agent when this applies, but there is no explicit guidance on when to use it versus alternatives such as rent_affordability, and no prerequisites or exclusions are given. Usage is inferable but not stated.

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