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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open world). The description adds meaningful context beyond them: the source of truth ('Etsy's published rates') and the modeling assumptions that bound the result. It stops short of describing the output shape or rounding/precision 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?

A single compact sentence that front-loads the subject (the fee components) and closes with the assumptions. No filler or redundancy.

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 read-only calculator with no output schema, the description reasonably implies a per-component breakdown and states its assumptions. It could be stronger by confirming the return shape (itemized vs. total) and that the result is in USD, but nothing essential is missing.

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% and all three parameters carry descriptions, so the schema does the heavy lifting. The description adds no extra parameter meaning such as currency handling or country-code matching behavior, so baseline 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 names a concrete resource ('Etsy's fees for one order in the seller's country') and enumerates the fee components it computes, so the agent knows exactly what will be produced. It doesn't explicitly contrast with the sibling tools, but those are all check/audit/idea tools, so confusion is unlikely.

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?

Scope boundaries are implied through the stated assumptions ('no sales tax on the order and no Offsite Ads'), which tells the agent when the numbers apply, but there is no explicit when-to-use or alternative guidance. Adequate but minimal.

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