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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is clear. The description adds value by detailing the exact calculation and the additional revenue output, which goes beyond the annotations but does not contradict them.

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, focused sentence that conveys the formula and the additional output without unnecessary words or repetition.

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 calculator with full schema coverage and an output schema, the description covers the essential behavior. However, it does not mention edge cases like the undefined scenario when price equals variable cost, which could be relevant in some contexts.

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 coverage is 100% with simple field descriptions. The description enriches these by defining the mathematical relationship among the parameters (price minus variable cost, divided into fixed costs), giving the agent a clear understanding of how inputs are used.

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 explicitly states the break-even volume formula (fixed costs divided by per-unit contribution) and notes it also computes revenue at that volume. This clearly distinguishes it from other break-even tools like option-breakeven or refi-breakeven, which have different contexts.

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 formula implies use for unit-level break-even analysis, but the description provides no explicit when-to-use or alternative comparisons. There is no stated exclusion, but the guidance is only implicit.

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