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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the restated 'Read-only' adds nothing; however the description does contribute beyond the schema by stating what the payload contains (websites, apps, YouTube channels/videos with spend and conversions) and that a visual card is also rendered — a side effect the agent would otherwise not know about. The default 30-day window is likewise disclosed.

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?

Purpose is front-loaded in the first sentence, followed by return contents, then behavior notes. Five short sentences with little waste; the only slack is the 'Read-only.' sentence, which duplicates the readOnlyHint annotation and could be dropped.

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?

No output schema exists, and the description compensates by naming the returned entities and metrics and mentioning the accompanying visual card. With 8 mostly optional, well-documented parameters, the remaining omissions (campaign_id semantics, folder-vs-account precedence) are minor.

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 88%, so the enum meanings for detail, language, date_range and the folder-vs-account distinction are already documented. The description only echoes the default period (LAST_30_DAYS) and adds nothing about campaign_id, which has no schema description at all — the one real gap it could have filled.

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 states a specific verb and resource ('see where Display, Video, Demand Gen and Performance Max ads were shown') and enumerates the campaign types plus return entities (websites, apps, YouTube channels/videos), so it is clearly distinct from search-oriented siblings like google_ads_search_terms. It stops short of naming the nearest alternative (e.g. google_ads_display_targeting, which covers where ads *can* run rather than where they *did*), leaving that distinction inferential.

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?

'Use this to see where ... ads were shown ... so the user can decide which placements to exclude' gives a concrete decision context and the default period is stated. There is no explicit when-not guidance and no sibling is named as the alternative path, so it is clear context without exclusions.

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