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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering safety and determinism. The description adds the formula and explicitly states the result is expressed as a percentage, which is useful behavioral context beyond the annotations. No contradiction.

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 sentence of 14 words that is front-loaded with the metric name and delivers the formula efficiently. Every word contributes value, with no repetition or filler.

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?

The tool is a simple calculation with two fully described parameters, an output schema present, and annotations covering safety. The description provides the formula and result format, making it complete for the agent to invoke correctly.

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 100% with both parameters described ('Annual pre-tax cash flow' and 'Cash invested'). The tool description essentially restates these definitions, adding only the relationship that cash flow is divided by cash invested. Per the rubric, baseline is 3 when schema coverage is high.

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 precisely defines cash-on-cash return as 'annual pre-tax cash flow as a percent of the cash invested,' which is a specific formula. This clearly distinguishes the tool from sibling metrics like ROI or cap-rate by stating the exact calculation.

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 tool name and definition: an agent would select this when asked to compute cash-on-cash return. However, it gives no guidance on choosing between related metrics (e.g., ROI, cap-rate) or when not to use it, so it only reaches the 'implied usage' level.

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