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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuine context beyond them by stating 'requires read scope' (an auth prerequisite) and scoping results to the billing period, but says nothing about the shape of the returned limits/counts or whether they are cumulative or per-period deltas.

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?

Two short sentences, zero filler, with the resource scope front-loaded and the auth requirement appended as a secondary constraint. Nothing here is redundant.

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 no-argument read tool with annotations covering the safety profile, the description tells the agent what data comes back (limits plus current counts) and over what window (the billing period). With no output schema, a brief note on the response structure would have closed the last gap.

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 zero parameters, so there is no parameter semantics to document and the baseline of 4 applies. The description correctly implies no arguments are needed by framing the call as a fixed-scope lookup.

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: 'get AI generation usage limits and current counts for the billing period.' The 'AI generation' qualifier meaningfully separates it from siblings like get_campaign_usage, get_contact_usage, and get_usage, though it never explicitly names those alternatives.

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?

Usage is implied by the scope ('AI generation', 'billing period'), so an agent can infer this is the per-period AI consumption view. However, there is no explicit when-to-use or when-not-to-use guidance versus get_usage or the other *_usage siblings.

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