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

Goes well past the readOnlyHint/openWorldHint annotations: it discloses the auth requirement (401 without a valid X-Api-Key), the throttling budget (30 req/min per key), that the budget is shared across the /v1/keys/usage routes, and the resulting error code (429 KEY_USAGE_RATE_LIMIT). It also specifies UTC calendar-day bucketing, which is behaviorally meaningful for interpreting the series.

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?

Front-loaded with the core purpose and logically ordered (what it returns, when to use it, alternatives, auth, limits). It loses a point for redundancy between the first and second sentences, which both say 'daily request counts over a trailing window'.

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 single-parameter read tool with no output schema, the definition still conveys return shape (daily time series, one point per UTC calendar day), auth, rate limits, and routing to alternatives. Nothing an agent needs to invoke 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?

Schema description coverage is 100% and the single parameter already documents default 30 and maximum 90, so the schema does the heavy lifting. The description only restates the trailing-N-days and UTC-end framing, adding no new meaning beyond the schema.

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?

Names a specific verb and resource ('Daily request counts for the authenticated key') plus the exact granularity of the window. It also explicitly separates itself from the current-day snapshot and raw-log endpoints, so an agent can distinguish it from lookalike siblings such as check_usage or get_key_activity.

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?

Gives a concrete use case ('plot usage trends or check rate-limit headroom over time') and states the two conditions that select an alternative: single current-day snapshot vs. raw request-by-request log. When-to-use and when-not-to-use are both covered.

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