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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered. The description adds valuable context by specifying the return fields and the endpoint. It omits whether the call is scoped to the current key's auth context (implied by 'current key'), which is a minor residual gap.

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 sentences, front-loaded with the payload description and the usage trigger. The endpoint reference is compact and useful; nothing is redundant with the title.

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 input schema parameters and no output schema, the description carries the burden of telling the agent what comes back — and it does so by enumerating the returned fields. Nothing needed to call and interpret this tool 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?

There are zero parameters, so parameter semantics have no surface area to cover. Score follows the 0-params baseline, and the description correctly does not fabricate any parameter detail.

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 states a precise verb+resource ('get usage' of the current key) and enumerates what is returned: tier, monthly cap, requests used/remaining, and reset time. It even includes the underlying endpoint (GET /v1/_meta/usage), leaving no ambiguity about what data is fetched.

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?

Explicitly names the trigger conditions: call when a request is rate-limited (HTTP 429) or when the user asks about their plan. This is exactly the when-to-use guidance an agent needs, and no sibling tool competes for that scenario.

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