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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds real value by disclosing the shape of the result (aggregates plus a per-hour/per-day series, top endpoints, common error statuses), which matters because no output schema exists. It stops short of stating whether results are aggregated over the whole range, whether top endpoints are ranked by count or latency, or any limits on the series.

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 dense sentence front-loads the scope then lists the payload fields, with no filler. It is a noun phrase rather than a clause, which slightly reduces immediate scannability, but every element earns its place.

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 one optional parameter, a fully described schema, and no output schema, the definition's main burden is describing what comes back, and it does so thoroughly. Only minor gaps remain: the range-to-granularity mapping and whether credits refer to billing consumption, plus no indication of response size for the 90d series.

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 coverage is 100% and the single 'range' enum is already documented as the 'Period to report', so the baseline is 3. The description's phrase 'over a period' and the 'per-hour or per-day series' hint at a granularity relationship, but it never says which range yields which granularity, leaving the only interpretive question about the parameter unanswered.

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 the resource (usage) and enumerates the exact content of the report: total calls, success rate, credits, latency, a time series, top endpoints, error statuses. An agent can distinguish this reporting tool from siblings like get_balance or get_billing by content, though it never states a verb and does not explicitly exclude those siblings.

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?

There is no when-to-use guidance: nothing tells the agent to prefer this over get_balance, get_billing, or get_log for volume/latency questions, and no prerequisites or exclusions are given. Usage is only implied by the enumerated metrics.

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