google_ads_get_pmax_placements

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

With no annotations, the description carries the full burden and does solid work: it explicitly says 'Read-only', identifies the exact data source, and warns that results are 'impressions only', preventing incorrect assumptions about available metrics. It doesn't disclose pagination or API-limit behavior, but for a read-only diagnostic tool this is meaningful disclosure.

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 a single, well-structured sentence that front-loads the most important facts: read-only, Performance Max, and placement diagnostics. Every part contributes value and there is no filler.

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?

Despite having no output schema, the description lists the return fields, making the result shape predictable. The only notable gap is that 'campaign context' is slightly vague and no explicit guidance is given for choosing this over google_ads_run_gaql or other PMAX siblings, but the description is otherwise sufficient for correct invocation.

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 high at 86%, so the parameters are already well-documented in the schema. The description adds context about the output fields but does not enrich parameter understanding, which is acceptable given the strong schema coverage.

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 names a specific resource (performance_max_placement_view), states the tool is read-only, and enumerates the exact returned fields: placement type, display name, target URL, campaign context, and impressions only. This clearly distinguishes it from sibling PMAX tools like google_ads_get_pmax_assets or google_ads_get_pmax_asset_diagnostics.

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 phrase 'Performance Max placement diagnostics' gives clear context for when to use this tool: when placement-level diagnostics from the performance_max_placement_view are needed. It does not explicitly name alternatives or state when not to use it, so it misses the top score, but the usage context is clear enough.

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