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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, covering the safety and side-effect profile. The description adds only the computational outcome (missed clicks, conversions, revenue), which is more purpose than behavioral detail, and it does not discuss rate limits, auth, or response behavior. With annotations doing the heavy lifting, a 3 is appropriate.

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 two short sentences and front-loads the core function. The second sentence is a pointer to an external full version; while not strictly necessary for tool invocation, it is concise and does not obscure the primary information.

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?

The tool is a simple four-parameter calculator with no nested objects or output schema. The description clearly states what is estimated, which is sufficient for an agent to know what to expect as output. Annotations cover the safety profile, so nothing critical is missing for correct invocation.

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%, so all four parameters are fully documented in the schema with clear descriptions (e.g., 'Current clicks per month'). The description does not add any parameter-level semantics beyond what the schema provides, 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 a specific verb ('Estimate') and resource ('missed clicks, conversions, and revenue from operating below 100% search impression share'), making the tool's core function clear. It does not, however, distinguish this tool from similar siblings like impression_share_opportunity_matrix or ppc_click_volume_predictor, so an agent must infer the difference.

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 description implies usage context by specifying the condition 'operating below 100% search impression share,' which tells the agent when the calculation is relevant. But it offers no explicit guidance on when to choose this tool over alternatives, nor any exclusions or prerequisites.

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