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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the safety profile is covered; the description adds genuinely new behavior by disclosing the join requirement (GSC queries matched against Ads search terms over the same period) and the classification threshold (top 3 organic). It does not state prerequisites such as needing both GSC and Google Ads connected, nor how rows are capped.

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 front-loaded sentence with no filler - the comparison is stated first, the three output categories follow. It is dense with parenthetical glosses, but every clause carries information an agent needs.

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?

For a 9-parameter, zero-required, read-only cross-source analytics tool with no output schema, the description is largely sufficient: it defines what the output sections are and what the comparison is anchored on. The gaps are secondary - no mention of prerequisites (both properties connected) or the effect of the limit parameter - which is why it is not a 5.

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 78% and the enum/label descriptions for detail, language, date_range, site, folder, and account are already documented inline. The description adds only the implicit constraint that both data sources are read over the same window; it says nothing about limit, detail, or how site/account resolve when multiple are enabled.

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?

Names a specific verb (compare) and two specific resources (Search Console queries vs Google Ads search terms) and then enumerates the three exact output segments: paid terms already ranking top 3 organically, paid terms with no organic presence, and organic winners with no ads. That is enough for an agent to distinguish it from gsc_queries, google_ads_search_terms, gsc_opportunities, or google_ads_wasted_spend 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 three listed segments implicitly define the triggers - cannibalization/savings, SEO gaps, and untapped organic winners - so an agent can match a user question to this tool. It stops short of explicit when-to-use/when-not language and never names an alternative sibling to defer to for a plain GSC or Ads term listing.

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