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

Annotations already indicate readOnlyHint and idempotentHint, so the description's value lies in stating the exact formula ('net income over shareholders' equity') and noting the output is a percentage. This adds meaningful behavioral context beyond the annotations, though it omits edge cases like zero equity.

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?

The description is a single, concise sentence that immediately communicates the metric, the formula, and the percentage output. It contains no superfluous words and is well-structured for quick consumption.

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 simple deterministic calculation with an output schema available, the description fully conveys the purpose and calculation method. It states the formula and the output format, leaving no critical gaps for the agent to misinterpret.

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?

The input schema provides 100% coverage with descriptions for both 'equity' and 'netIncome.' The tool description only restates these terms within the formula, adding no new semantic information beyond what the schema already supplies, so the baseline score applies.

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 clearly defines the tool as 'Return on equity, percent: net income over shareholders' equity,' stating both the metric and the exact formula. This distinguishes it from sibling metrics like ROA (return on assets) and ROI (return on investment) by explicitly referencing equity.

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 description implies usage (calculate ROE) but provides no explicit guidance on when to choose this tool over alternatives like ROA or ROI. There are no stated exclusions or references to sibling tools, leaving the agent to infer the appropriate context.

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