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

The description adds meaningful behavioral context beyond the readOnlyHint annotation by detailing what the report contains and noting that it is free to call. It does not describe response format or potential pagination, but the annotations already signal safety and open-world output.

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?

Three sentences each carry purpose: what the tool reports, when to use it, and the cost implication. The first sentence is dense with an em-dash and a long list, but it is still readable and front-loads the core 'what you have spent and what is left' message.

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 usage report with readOnlyHint and openWorldHint already set, the description covers everything an agent needs: the report's contents, the recommended timing, and that it is free. No output schema exists, but the description sufficiently describes the returned information without needing to enumerate fields.

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 the input schema is fully complete by default. The description adds value by explaining what data the report exposes, which is more than the schema can convey.

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 clearly identifies the tool as an account usage and limits report, enumerating what it covers: renders, billable units, cost, free-tier allowance, monthly spend cap, and trial render count. The imperative 'Check it' makes the read action explicit, and this is clearly distinct from the sibling creation, rendering, and template tools.

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 a specific trigger for use: 'Check it before a large batch.' This is clear contextual guidance, though it does not explicitly name alternatives or state when not to use the tool. The sibling list contains no overlapping read-only usage tool, so the guidance is sufficient.

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