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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered structured-side. The description adds the framing that this is a counterfactual opportunity estimate against a 100% impression share baseline, which is useful context, but it says nothing about input assumptions, precision, or failure modes. Adequate but not 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?

The first sentence is well front-loaded and wastes nothing. The second sentence is a promotional link to an external site that does not earn its place in a tool definition, marginally diluting the otherwise efficient structure.

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 three-parameter, no-output-schema calculator, the description adequately conveys the purpose, the input conditions, and the nature of the result (missed conversions and revenue). It is complete enough to invoke, with only the sibling-routing gap remaining.

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 description coverage is 100% with three simple, self-explanatory numeric parameters (conversions, impressionSharePct, valuePerConversion), so the schema carries the load and the baseline of 3 applies. The description adds no units, ranges, or baseline assumptions beyond what the schema already says.

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?

States a specific verb and outcome ('Estimate missed conversions and revenue') tied to a specific resource and condition ('operating below 100% impression share on a search campaign'). However, it offers no differentiation from the near-identical sibling google_search_impression_share_value_estimator, so an agent cannot route between the two from this text alone.

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 explicit when-to-use guidance, no prerequisites, and no mention of an alternative. The second sentence only points to a web version of the calculator, which does not help an agent decide whether to call this tool versus the sibling impression-share estimator.

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