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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds that it also returns revenue and target-profit units, but omits formatting behaviour (currency display) and the edge case where variable_cost_per_unit ≥ price_per_unit makes break-even undefined — relevant since the schema only constrains price to be > 0.

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 front-loaded sentence with no filler; the dense list of inputs and outputs is appropriate for a calculator. Slightly harder to scan than a short two-sentence split between inputs and outputs, but nothing is wasted.

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 bears the burden of describing return values; it names three outputs but not their shape (flat object? per-currency strings? rounded?), and gives no guidance on invalid input combinations. Adequate but with clear gaps for a 5-parameter financial 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 description coverage is 40%, so the description must compensate: it names fixed costs, price, variable cost per unit and target profit, and clarifies that contribution margin is a derived output rather than an input. That is useful, but it doesn't state units (per-period? absolute?), how currency affects results, or that target_profit is optional.

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 verb ('Calculates') plus the exact outputs (break-even units and revenue, units for target profit) and the inputs driving them. 'Break-even' is self-distinguishing from siblings like unit_economics or max_affordable_cac, though the description never names an alternative explicitly.

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?

There is no when-to-use / when-not-use guidance and no mention of how this differs from adjacent finance tools such as unit_economics or growth_projection. Usage is only inferable from the tool's name.

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