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

With no annotations, the description carries the full behavioral burden. It does disclose the metric set and that the scope is a time window on the customer's account, which is genuine value given there is no output schema. However, it says nothing about whether results are per-campaign rows or aggregated, pagination/row limits, permission requirements, or the read-only nature of the call.

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 first and the metric inventory after. It is appropriately sized and wastes no words, though the metric enumeration is dense enough that it reads as a list rather than structured guidance.

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 3-parameter read tool with no annotations and no output schema, the metric list is a reasonable partial substitute for a return-value schema. But the description leaves the agent guessing about result granularity, filtering behavior of campaignId/channelType, and default time range beyond the schema default.

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 only 33%: campaignId is documented in the schema while timeRange and channelType carry only enums. The description's phrase 'for a window' loosely gestures at timeRange but adds no meaning for campaignId (single-campaign filter) or channelType (channel filter), so it fails to compensate for the coverage gap.

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 ('Get Google Ads campaign insights') and enumerates the exact metrics returned, which is far more informative than the title alone. It is distinguishable from list_ad_campaigns (which enumerates campaigns) and google_ads_manage_campaign (which mutates), though it does not name those siblings 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?

There is no when-to-use guidance and no alternatives named. An agent cannot tell from the text whether to reach for this versus list_ad_campaigns, google_ads_manage_campaign, or google_analytics_get_overview when it needs performance data; usage is only loosely implied by 'campaign metrics'.

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