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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds useful context about the 30-day lookback and returned breakdowns, but does not discuss rate limits, authentication, or other behavioral traits. This aligns with the calibration baseline for annotation-covered read tools.

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 front-loaded sentence contains every meaningful detail: credit balance, reserved holds, available credits, per-verb usage, and the 30-day window. There is no repetition of the title or the parameter schema, and 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?

For a zero-parameter, read-only tool with no output schema, the description fully enumerates what will be returned. There are no required inputs, side effects, or alternatives that need explanation, so nothing essential 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?

The tool has zero parameters, so there is nothing for the schema to document. The description adds value by enumerating the kinds of results the agent should expect, which is the only semantic dimension available here.

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 leads with the verb "Returns" and names the exact resources: credit balance, reserved holds, available credits, and per-verb usage. This clearly distinguishes it from all listed sibling tools, none of which target credit or usage data.

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?

The description makes the tool's context clear: call it when you need credit balance, holds, available credits, or 30-day per-verb usage. It does not explicitly name alternatives or exclusions, but no sibling tool competes for this purpose, so the usage context is sufficient.

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