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

With no annotations, the description carries the burden. It transparently discloses the core behavior (price back-calculation, shipping comparison) and notes it is browser-based. However, it does not reveal assumptions like fee rates or output format, leaving some ambiguity for a calculator tool.

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 a single, concise sentence that front-loads the core function and mentions the shipping comparison. Every part adds value with no filler.

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 zero-parameter, browser-based calculator with no output schema, the description is reasonably complete. It explains what it does and a key feature, though it does not detail return values or fee assumptions, which are minor for this type of tool.

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 baseline per rules is 4. The description adds no parameter-specific info, but none is needed since the input schema is empty.

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 states specifically that it back-calculates an optimal price from a profit rate and compares shipping-included vs. separate shipping. This is a clear verb+resource+scope combination that distinguishes it from sibling tools like 'mercari-calculator' or 'mercari-shipping-compare'.

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?

No guidance is provided on when to use this tool versus alternatives. The phrase 'Browser-based tool' only implies an interactive nature, but there is no explanation of when to choose this over mercari-calculator or other related tools.

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