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

Annotations already establish read-only, non-destructive, closed-world behavior, so the safety profile is covered. The description adds genuinely useful behavior context beyond that: the direction of the result (lower value means more rent per dollar of price), which is the key interpretive trait for this metric.

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?

Two short sentences, formula first and interpretation second, with no filler. Every clause carries information.

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?

With no output schema, the description correctly supplies the return meaning (a ratio plus its interpretation). It does not mention edge cases such as zero rent or non-numeric input, a minor omission for a pure two-parameter calculator.

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 coverage is 100%, so both parameters are documented in the schema, warranting the baseline of 3. The description adds the derivation rule but introduces a gap: it says 'annual gross rent' while the schema parameter is 'Monthly rent', and it never explains that the monthly input is annualized, leaving a small mismatch for the agent to reconcile.

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 metric and the exact formula (price divided by annual gross rent), so an agent knows precisely what is computed. Against a sibling list of ~35 unrelated calculators, this is unambiguous and self-identifying.

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?

Usage is implied by the formula rather than stated: the description never says when to prefer this over related rental metrics (e.g., cap rate or ROI tools). For a single-purpose calculator with a fixed formula, the implied usage is adequate, but no contextual or exclusion guidance is offered.

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