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

Annotations already declare readOnlyHint=true, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds the return fields (units, revenue, contribution margin), which the absent output schema would otherwise hide, but says nothing about defaults being applied when inputs are omitted or about currency affecting the results.

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 tight sentences with the motivating question front-loaded, followed by inputs and outputs. The trailing marketing URL is minor padding but does not obscure the core content.

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 usefully enumerates what comes back, and all four parameters are covered by the schema. It stops short of explaining default-driven behavior (e.g. a call with no arguments returns the 12000/50/30 case) or how currency shapes the outputs.

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%, so the schema already documents fixed, price, variable and the currency enum. The description merely echoes three of the four parameters and adds no format, unit or default semantics, so the baseline of 3 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 states a specific question ('How many units must you sell before you make a profit?') and names both the inputs (fixed, price, variable) and the outputs (break-even units, revenue, contribution margin). It is clearly distinct from siblings like profit_margin_calculator or markup_calculator, though it never explicitly contrasts itself with them.

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 only implied by the list of inputs; there is no statement of when to choose this tool over adjacent ones such as profit_margin_calculator or roi_calculator, and no prerequisites or exclusions. An agent must infer the scenario entirely.

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