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

With no annotations, the description must disclose behavioral traits, but it only states that the tool is browser-based. It does not explain how it accepts input (since the schema has zero parameters), what the return format is, or any limitations or rate handling. This is a significant gap for a tool with no structured safety hints.

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, front-loaded with the core function and followed by the platform note. Every word contributes value; there is no unnecessary repetition or 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 browser-based calculator with no parameters, no annotations, and no output schema, this description is reasonably complete. It states what the tool does and its platform, which is sufficient for an agent to launch it. However, it could benefit from noting that it involves no direct parameter input since the schema is empty.

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 schema has 0 parameters, so the baseline is 4. The description adds meaning by specifying the input (RPP advertising cost) and the derived outputs (CPC, ROAS, break-even), which helps the agent understand the tool's data flow even though no formal parameters exist.

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 uses a specific verb (計算 = calculate) and clearly states the resource (RPP advertising cost) and the outputs (CPC, ROAS, break-even). This distinguishes it from sibling calculators like rakuten-fee-calculator or yahoo-auction-calculator by naming the exact ad product and metrics.

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 intended use case is implied from the calculation targets, but there is no explicit guidance on when to use this tool versus alternatives. It does not mention any exclusions or prerequisites, though the phrase 'Browser-based tool' hints at a client-side execution context.

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