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

Annotations already declare readOnlyHint, idempotentHint, non-destructive, and closed-world, so the safety profile is fully covered. The description adds that it produces a verdict on whether the campaign covers its product cost, but it does not describe the shape or semantics of that verdict or how currency affects the numbers. Given annotations carry the safety burden, this is adequate rather than rich.

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?

One front-loaded sentence that names the computation, the derived metric, and the conclusion. No filler, no repetition of the title.

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?

With no output schema, the description must convey what comes back, and it does name both computed values plus a coverage verdict. It stops short of explaining the verdict's exact wording, formatting, or the relationship between the two returned ROAS figures, which leaves a small gap for a tool whose only output signal is prose.

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%, so all four parameters are already documented in the schema, including the INR default. The description maps the inputs to their roles ('break-even ROAS implied by gross margin'), which adds slight meaning beyond the schema but no format or edge-case guidance.

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 a specific verb-and-resource pair: it computes ROAS and break-even ROAS from named inputs and adds a coverage verdict. That distinguishes it from sibling metrics tools like acos_check or campaign_roi by formula, though it never names those siblings explicitly.

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?

Usage is implied by the formula (ROAS inputs in, break-even comparison out), but there is no explicit guidance on when to pick this over acos_check, campaign_roi, or break_even. An agent must infer the choice from the input vocabulary.

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