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

Annotations already establish read-only, idempotent, non-destructive behavior, so the description correctly spends its words elsewhere: it discloses the Last Price credential requirement and the concrete failure mode (403 for unclaimed sandbox keys from self-registration). It does not describe response shape or any rate limits, keeping it short of 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?

The core operation and default period are front-loaded in the first clause, followed by the enumerated metrics and then the preconditions. Every sentence carries distinct information with no restatement of the tool name or annotations.

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 compensates by enumerating the aggregated metrics, and it covers the two realistic call-time blockers (credential type, unclaimed workspace). The missing piece is differentiation from get_usage_breakdown, which an agent needs to avoid picking the wrong usage 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?

Schema description coverage is 100%, and the description only restates the period/default behavior already documented on start_date and end_date. It adds no syntax, format, or edge-case details beyond the schema, so the baseline 3 is appropriate.

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 ('Total') and resource ('your workspace's priced calls') plus a default time window, and enumerates exactly what is aggregated (requests, units, compute time, cost, cached/prepaid calls, unbilled remainder). It does not, however, distinguish itself from close siblings like get_usage_breakdown or list_usage_events.

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?

Default scope ('this calendar month by default') and prerequisites are stated, which implies when the tool applies. But there is no explicit guidance on when to prefer this over get_usage_breakdown, list_costs, or list_usage_events, leaving the agent to infer the boundary.

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