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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds useful behavioral context beyond that: the output contents (RPM range, monthly/yearly ranges, model used, calculator link) and the scope boundary that sponsorships/memberships are excluded. It stops short of stating the model's assumptions or accuracy limits.

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?

Three short sentences, front-loaded with what it computes and returning before the scope caveat and sibling pointer. No filler, every clause carries 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?

There is no output schema, so the description carries the burden of describing the return value, which it does by enumerating RPM range, monthly/yearly USD ranges, model used, and calculator link. It leaves only minor gaps such as the assumptions behind the RPM estimate.

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% and all three parameters (niche, shorts, monthly_views) are documented in the schema itself, including the niche enum and the interaction ('Ignored when shorts=true'). The description adds no parameter-level detail beyond the schema, so the baseline 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?

States a specific verb and resource ('Estimate YouTube ad revenue for a channel') plus the key input ('from its monthly views'), so the agent knows exactly what the tool computes. It also delimits itself from the sibling creator_monetization, making the scope unambiguous.

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?

Explicitly names the alternative and the condition that selects it: 'Use creator_monetization for the underlying RPM tables and program requirements.' It also states a clear scope exclusion ('Ads only, no sponsorships or memberships'), so an agent knows when this tool is the wrong one.

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