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 covered. The description adds that the estimate is a calculation with two alternative formula paths, but says nothing about return shape, rounding, or whether inputs are validated/clamped.

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?

A single front-loaded sentence with the resource, the purpose, and both input paths; no filler and no restatement of the title.

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?

With no output schema and six parameters, the description leaves the agent guessing what comes back (a single revenue figure? a breakdown?) and in which currency relative to the input currency. Adequate for invoking the tool, but thin for interpreting 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 coverage is 83%, so the per-parameter docs (RPM, CPM, fill rate, currency default INR) already carry most of the load. The description still adds genuine value by grouping the parameters into coherent modes — pageviews+page RPM vs pageviews+ads_per_page+CPM+fill_rate — a pairing the schema only hints at with 'Use this or cpm'.

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 ('Estimates display ad revenue for a website or blog') and names the two calculation paths, which distinguishes it from siblings like youtube_earnings or instagram_earnings only implicitly via 'website or blog'. Clear but does not explicitly contrast with the nearest siblings.

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 phrase 'or from ad impressions per page, CPM and fill rate' implies two alternative input modes, so an agent can infer which mode to pick. But there is no explicit when-to-use/when-not guidance, no mention of prerequisites, and no pointer to alternatives such as ad_budget_planner.

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