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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds real value by disclosing the calculation model (the 55% long-form creator share and the RPM-vs-CPM branch). However, it never says what the response contains — no mention of the earnings figure, watch-hours result, or gap to the Partner Program threshold — so the returned shape is opaque.

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 dense sentence that front-loads the primary outcome (earnings) before the secondary one (watch hours). Every clause carries information, though the parenthetical formula makes it noticeably harder to scan.

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 is the only place the return values could be described, and it does not describe them. It also doesn't explain that watch hours depend on avg_view_duration_minutes or what the YPP threshold comparison yields. Adequate to call, insufficient to predict the result.

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 each of the 7 parameters is already documented, including 'Use this or cpm' and the currency default of INR. The description reinforces the cpm/rpm relationship and introduces the 55% share constant, but adds little parameter meaning the schema does not already carry.

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 ('Estimates') and a precise resource ('YouTube ad earnings' and 'watch hours'), with the two input paths (RPM, or CPM x monetized playback % x 55% share) named. It is clearly distinct from the nearest sibling, instagram_earnings, but never names or routes to any alternative tool 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 through the two calculation paths ('RPM from YouTube Studio' vs 'CPM, monetized playback % and 55% share'), which tells the agent which inputs to supply together. There is no explicit when-to-use, when-not-to-use, or comparison against instagram_earnings or website_ad_revenue.

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