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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description goes well beyond them: it discloses the consequence of exhaustion (all credit-costing X activity pauses until next month or a new seat) and enumerates per-action costs. It stops short of describing what the response looks like (pool size vs. per-action breakdown vs. reset date), but that is a minor gap given zero parameters.

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 opening sentence is a heavily em-dashed run-on that buries the actual function behind the billing model, and the cost table is a third of the text for a zero-param read. All the content is relevant, but the front-loading is weak — the strongest line (when to check) sits second.

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 tool with annotations covering safety and no output schema, the description supplies the domain model, the trigger condition, the consequence of empty pools, and the unit costs an agent needs to answer 'what fits'. Nothing needed to call it correctly 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 takes no parameters, so the baseline of 4 applies. The description correctly describes a parameterless check rather than implying hidden inputs such as an account or date selector.

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?

Together with the name and title, the description makes clear this reports the monthly X credit pool (1 credit = 1 cent) and its cost model. It never states plainly 'returns the remaining credit balance', so the core object of the verb is inferred from the billing explanation rather than asserted. Sibling quota tools (get_message_usage, get_image_quota) are not named for contrast.

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?

'Check this BEFORE scheduling a batch of posts to X or turning on X automations' gives an explicit trigger condition, and it says why (so you can tell the human what fits). No when-not condition or named alternative is given, which keeps it short of a 5.

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