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

No annotations are provided, so the description must fully disclose behavior. It only mentions 'Browser-based tool' and instant calculation, but does not explain how the tool is invoked, whether user input is required (the schema has no parameters), what the output/return behavior is, or any limitations. This leaves significant opacity for an agent.

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 sentence that front-loads the core functionality (ad cost to ACoS/ROAS/break-even CPC) and appends the browser-tool nature. Every word earns its place; there is 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 0-parameter browser-based calculator with no output schema, the description is thin. It communicates what is calculated but not the user workflow (e.g., how the agent should interact with the browser tool, what the user will see, or how results are delivered). Given no annotations and no output schema, the description should provide more operational context.

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 0 parameters, so schema coverage is 100% and the baseline is 4 per the rubric. The description adds no parameter details, but none are needed; it does not clutter with irrelevant information.

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 calculates ACoS/ROAS and break-even CPC from advertising cost, using the specific verb 算出 (calculate). The input-to-output mapping (広告費→...) is explicit, and the metrics named distinguish it from sibling calculators.

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 usage is implied by the metric names (ACoS, ROAS, CPC), but the description provides no explicit guidance on when to use this tool over alternatives like amazon-fba-calculator or rakuten-fee-calculator. No when-to-use or when-not-to-use conditions are stated.

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