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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so safety is covered; the description goes beyond them with real behavioural constraints — a fixed 7-day window, local-hours bucketing, and DST days yielding 23 or 24 buckets. It stops short of describing shape/ordering of the returned buckets, which keeps it at a 4 rather than a 5.

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?

Front-loaded with the core definition, then usage, then the data-availability constraint, then the DST edge case. Every sentence carries decision-relevant information and none is 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?

With no output schema, the description still supplies what an agent needs: window, resolution, timezone basis, DST edge case, and an explicit instruction for the unsupported hourly spend/margin/ROAS case. Nothing consequential is left unspecified for a zero-parameter read tool.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a no-parameter tool applies. No misleading parameter language is present.

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+resource with explicit scope: 'Revenue per hour of the local day, over the last 7 days.' The hourly/local/7-day framing cleanly separates it from sibling aggregates like get_sales, get_series or get_sales_breakdown without the agent needing to open any schema.

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?

Gives positive selection criteria ('when the question is about time of day — which hours sell, when a spike happened within a day') and a hard exclusion ('REVENUE ONLY'), plus a fallback behaviour when asked for hourly spend, margin or ROAS. This is explicit when-to-use and when-not-to-use guidance rather than implication.

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