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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the 'Read-only' phrase is confirmatory rather than additive. The genuinely new behavioral facts are 'no paging' (the full usage snapshot is returned in one response, so no follow-up calls are needed) and that figures are scoped to the current quota window only. Return-field list substitutes for the missing output schema.

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?

Two sentences plus a scope note, front-loaded with what is returned before the usage trigger and the disambiguation. Every clause carries information an agent would otherwise have to guess.

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 carries the return-value burden itself and does so by enumerating the response fields. Combined with the read-only and no-paging notes, nothing material for correct invocation is missing.

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?

This is a zero-parameter tool, so the schema coverage baseline is 4. The description correctly implies no input is needed, though it never states outright that the quota window is taken implicitly from the authenticated account rather than being selectable.

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 opens with a concrete verb+resource ('Return the authenticated account's current API usage for this quota window') and then enumerates exactly what comes back: plan, period start/end, requests used/limit/remaining, and requests per minute. The trailing NOTE explicitly bounds the scope against the sibling tools in the contract family, so an agent can route correctly without opening a 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?

"Use it when the user asks how many calls remain or which plan they are on" gives explicit trigger phrasing, and the NOTE rules out confusing this with contract data. No alternative tool is named for the same need, but none exists in the sibling list, so there is little left to infer.

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