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

With no annotations, the description carries the burden of behavioral disclosure. It notes that the tool is 'browser-based,' which is a useful trait. It also reveals the calculation components (fee, shipping, profit, premium comparison). However, it does not mention how the tool handles inputs, whether it produces a simple output, or any limitations. The transparency is adequate but minimal.

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?

The description is one compact line, front-loaded with the core purpose. Every element (fee rates, shipping, profit, premium comparison, browser-based) adds value. There is no wasted text.

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 browser-based calculator with no schema or annotations, the description covers the essential context: what it calculates, the fee rates involved, and a key comparison feature. It does not detail the output format or steps, but these are likely self-explanatory for a calculator. The description is sufficiently complete for the tool's simplicity.

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?

The tool has zero parameters, so the description does not need to explain schema fields. However, the description adds semantic meaning by naming the exact fee rates (10%/8.8%) and the shipping cost as factors, as well as the premium membership comparison. This helps the user understand what inputs the calculator likely expects, despite the empty schema.

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 clearly states the tool's function: calculating profit from Yahoo Auction fees (10%/8.8%) and shipping, plus a premium membership comparison. While it lacks an explicit verb like 'calculate,' the noun phrase and arrow notation make the purpose clear. It distinguishes itself from sibling calculators like mercari-calculator and rakuten-fee-calculator by citing specific Yahoo Auction fee rates.

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 description gives context (Yahoo Auction, premium membership comparison) but does not explicitly state when to use this tool over alternatives. It provides no criteria or scenarios, and does not mention any alternative tools. Users must infer its purpose from the name and title.

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