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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and idempotency are covered. The description adds only the content of the counters; it says nothing about default windowing behavior, aggregation granularity, or the shape of the series/totals split beyond the field names.

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 short sentence with the resource front-loaded and no filler. It is efficient, though the verbless fragment leaves the agent to infer that it returns data rather than describing the Overview UI.

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?

All three parameters are fully described and annotations carry the safety profile, but with no output schema the description should clarify the return shape (e.g. per-day series vs. totals, the meaning of 'selected' and 'can_edit' in the fields enum). 'Daily counters' gestures at it without closing the gap.

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 100%, and the schema already documents days (default 30, max 365), the fields enum, and project_id sourced from list_projects. The description adds no syntax, defaults, or interaction rules, so the baseline 3 applies.

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 ('Daily counters behind Overview') and enumerates the metrics returned (posts, emails, calls, spend, tokens), so an agent knows this is an aggregate metrics read rather than a record fetch. It does not differentiate itself from look-alikes such as get_inventory_overview or google_ads_campaign_stats, which keeps it below a 5.

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?

Tying the tool to the 'Overview' surface implies its usage context, but there is no explicit when-to-use statement and no mention of when to prefer google_ads_campaign_stats or get_inventory_overview instead. Usage must be inferred from the metric list.

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