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

Beyond the readOnlyHint and openWorldHint annotations, the description adds useful behavioral detail: the date window means the last N full days up to yesterday and excludes today, results are sorted by cost descending, and workspace is optional when only one workspace exists. It does not discuss authentication or rate limits, but for a read-only reporting tool the added context is substantive.

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 front-loaded with the main purpose and then supplies date interpretation, returned fields, sorting, and workspace notes. It is reasonably efficient, though listing every returned field is somewhat redundant given that an output schema exists.

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 an output schema present and read-only annotations provided, the description covers the essential context: what is measured, over what date window, how results are sorted, and the workspace condition. The main remaining gap is campaign_id semantics, but overall it is complete enough for an agent to invoke the tool correctly.

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 0%, so the description must carry parameter meaning. It explains the days parameter well (last N full days, excluding today) and explains workspace as a slug that is optional when there is only one workspace. The campaign_id parameter is only implied by 'optional je Kampagne' and its format or exact role is not clarified.

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 resource and metric domain: performance of PMax asset groups over the last N days, including impressions, clicks, cost, conversions, and Ad Strength. It makes clear that this is asset-group-level performance, which is distinguishable from sibling tools such as ads_campaign_performance or ads_ad_performance.

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?

It specifies the reporting window and that campaign filtering is optional, which implies the usage context. However, it does not explicitly say when to use this tool instead of sibling performance tools like ads_campaign_performance or ads_list_asset_groups, leaving the agent to infer the choice from the resource name.

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