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

Annotations already declare readOnlyHint=true and idempotentHint=true, so safety is covered. The description adds behavioral context beyond annotations: it states the calculation is restricted to entered inputs, lists the specific calcued outputs, and explicitly disclaims forecasting. This is useful and consistent with the annotations, though it does not go into formula details or error behavior.

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, no fluff, and the scope is front-looaded with 'Calculate only'. The second sentence earns its place by explicitly ruling out a plausible misuse. This is an example of conciseness that improves usability.

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 four-parameter calculator with an output schema available and read-only/idempotent annotations, the description is largely complete: it identifies inputs, outputs, and what the tool will not do. It does not explain the exact formula or plan-pricing logic, but those are likely visible in the output schema or not needed to invoke the tool correctly. The main gap is slightly richer parameter guidance, already accounted for in parameter semantics.

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 0%, so the description must compensate. It partially does so by mapping 'time savings' to hoursSavedPerMonth and 'plan cost' to planId, and it names the outputs. However, it does not elaborate on the semantics of hourlyCost or currency, and the relationship between planId and plan cost is only implicit. The self-explanatory parameter names and enums help, but the description itself leaves some parameter meaning under-specified.

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 states a specific verb ('Calculate') and a precise resource scope ('DigitalPublic time-value ROI'), then narrows it further to time savings, plan cost, net value, and break-even hours. The explicit negative clause 'It never forecasts sales or advertising performance' clearly distinguishes this tool from any predictive/commercial tool among the siblings.

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 makes the intended use clear: this tool only values entered time-savings, plan cost, net value, and break-even hours. It also supplies an explicit exclusion ('never forecasts sales or advertising performance'), so an agent knows not to use it for forecasting. It does not name a specific alternative sibling, but the context and negative scope still provide solid guidance.

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