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

Annotations already declare readOnly and idempotent behavior. The description adds useful context by disclosing the output scope (per campaign plus _summary) and batched execution via customer_ids, which goes beyond the annotations.

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?

The description is two concise sentences with no filler or redundancy. Front-loaded with the core purpose and followed by the bulk support detail, it earns every sentence.

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 read-only summary tool, the description covers core metrics and batch capability, but it omits details like timezone/scheduling for 'today' and how account/customer_id/customer_ids interact. The lack of an output schema heightens the need for such parameter-scoping information.

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?

With schema description coverage of 0%, the description must compensate for under-documented parameters. It only explains that customer_ids is for batched execution; it does not clarify the distinction or relationship between account, customer_id, customer_ids, or whether any are required.

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 clearly states it returns today's Google Ads performance with specific metrics (cost, impressions, clicks, conversions, ROAS) per campaign plus a summary. The 'Today' qualifier and metric list distinguish it from broader sibling tools like google_ads_performance or google_ads_roas.

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 description gives a helpful usage cue by noting bulk support for customer_ids, implying it can be used for batched execution. However, it does not explicitly state when to prefer this tool over alternatives like google_ads_performance or google_ads_campaigns, nor does it mention exclusions or prerequisites.

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