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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so safety is fully covered. The description does add value beyond them by disclosing that results are scoped to the bearer token rather than an arbitrary account and that usage is resolved per period. What "conservation totals" and "exact catalog lineage" operationally mean is never explained, leaving the behavioral picture partially opaque.

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?

It is a single sentence with no filler, which is structurally efficient. But the density of undefined terms means brevity comes at the cost of comprehensibility, and the most actionable detail (bearer scoping) is not front-loaded.

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?

An output schema and annotations cover return shape and safety, lowering the bar. Still, for a tool whose selection hinges on being distinguishable from mrr_summary, the description supplies neither usage routing nor parameter meaning, so key gaps remain.

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?

There is one required parameter, account_id, with 0% schema description coverage, so the description carries the entire burden. It never mentions account_id or clarifies how an explicit account identifier interacts with the "bearer-owned" scoping claim, which is exactly the ambiguity an agent would trip on.

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 and resource ("Return ... usage") and gestures at scope via "bearer-owned" and "period-resolved." However, the core framing is buried under unexplained jargon ("catalog lineage," "conservation totals"), so an agent cannot immediately tell what the payload actually contains or how it differs from the nearby mrr_summary tool.

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 statement, no preconditions, and no mention of the closest alternative, mrr_summary, which also summarizes billing-period data. The agent must infer selection from the name alone.

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