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

The description adds no behavioral context beyond the readOnlyHint annotation. It does not mention the formula (revenue/adSpend), edge cases like zero ad spend, or the output format despite the ambiguous 'percentage' hint. With readOnlyHint already provided, the description contributes nothing extra.

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 short but not concise: it repeats 'ROAS' unnecessarily and includes a confusing parenthetical. Every word does not earn its place, and the structure is less effective than a simple 'Calculate ROAS as revenue divided by ad spend.'

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 read-only calculator, the schema plus readOnlyHint cover most needs. However, the lack of an output schema means the description should clarify the return format; the vague 'percentage' hint is incomplete. The description is minimal but not fully inadequate, so a 3 is appropriate.

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% with descriptive parameter names and descriptions ('Revenue from ads', 'Ad spend'). The description adds no additional parameter meaning, but the schema already fully explains both parameters, so the baseline of 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 states the tool calculates ROAS, which is a specific verb and resource, but the phrase 'Calculate ROAS, ROAS (percentage)' is redundant and does not distinguish it from sibling calculators like cpc-calculator or ctr-calculator. The repetition and ambiguous 'ROAS (percentage)' weaken clarity.

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?

There is no guidance on when to use this calculator versus similar siblings (e.g., cpc-calculator, cpm-calculator). The description gives no context about scenarios where ROAS calculation is appropriate, nor does it exclude alternatives.

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