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

The annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, but the description adds substantial context: the 30-day lookback, daily breakdown, client name/tier, and the hard scope restriction to the calling key. These details tell the agent what data will be returned and what access is impossible beyond the safety hints.

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 front-loads what is returned, then states the scope restriction, then gives use cases in compact sentences. Every sentence adds decision-relevant information with 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?

With an output schema, no input parameters, and rich annotations, the description supplies the remaining context an agent needs: time window, scope, return dimensions, and typical use. No important calling condition appears to be 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?

The input schema has zero parameters and is an empty object, so there are no parameter semantics to document. The baseline for zero-parameter tools is 4, and the description appropriately avoids inventing parameters.

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 verb and resource: usage of the calling API key over the last 30 days, including request count, error count, latency, client name, and tier. It also explicitly rules out legislative data, which separates it from the many legislative list_* and get_* 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?

It gives concrete reasons to call it, such as checking quota proximity and explaining error bursts, and it states a clear boundary: there is no way to read another client's usage. It also steers away from legislative-data tools, though it does not name a specific sibling alternative for quota-related questions.

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