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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description adds the computation semantics (ad-equivalent spend = clicks x CPC, subtract branded share), which is useful, but says nothing about output format, rounding, or edge cases such as a 0% or 100% branded share.

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 operative definition is front-loaded in a single dense sentence with no filler. The trailing 'See the full version at <URL>' sentence is promotional rather than actionable for an agent, so it doesn't fully earn its place, but the total size stays small.

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?

There is no output schema, so the description carries the burden of explaining what the tool returns, and it only loosely gestures at 'ad-equivalent spend' and a 'non-branded portion' without naming concrete outputs. For a read-only calculator this is workable but leaves the agent guessing about the response shape.

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 baseline is 3, but the description goes further by explaining how the parameters relate (clicks x CPC gives ad-equivalent value; brandedSharePct is the portion 'you would likely get for free anyway'). That relationship is not expressed in the schema and helps the agent reason about the inputs.

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 names a specific computation (clicks x CPC ad-equivalent spend) on a specific resource (organic search traffic) and adds a scope qualifier (non-branded/defensible SEO value) that separates it from the branded-inclusive sibling google_search_impression_share_value_estimator. An agent can identify the tool's output without opening the schema.

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 frames the purpose (valuing organic traffic, isolating defensible non-branded value) but never states when to choose this tool over the many sibling calculators (e.g., google_search_impression_share_value_estimator, click_volume_predictor) or what inputs are prerequisites. Usage is implied by the calculation rather than declared.

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