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

Annotations already declare readOnlyHint=true, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description usefully adds that the computation is deterministic and requires no signup/auth, but says nothing about units, currency, rounding, or what the result represents.

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, front-loaded sentences with no filler; the core definition comes first and the operational note second. It is tight, though the second sentence serves marketing more than invocation.

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 7-parameter calculator with no output schema and 0% parameter documentation, the description is thin. It should at minimum explain the return value (net contribution figure) and the interpretation of percentage/currency inputs; neither is present.

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% across 7 parameters, so the description must carry the burden and it does not. It gestures at cost categories (goods, fees, ads, shipping) but never clarifies that platformFeePct is a percentage, what units shippingCharged uses, or whether adCost is per-unit or total.

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 names the resource precisely ('ecommerce net contribution after goods, fees, ads and shipping'), which tells an agent exactly what is computed. However, it never distinguishes itself from the sibling penny_margin or penny_target_price, which an agent could easily mistake for the same calculation.

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 statement of when to use this tool versus penny_margin, penny_campaign_economics, or penny_target_price, and no prerequisites or exclusions. The 'Free, no signup' note is a convenience claim, not usage guidance.

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