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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds a genuine behavioral constraint the annotation does not: it requires an organization key. It stops short of describing response format, quota windowing, or rate limits.

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 tight clauses, front-loading the returned data ahead of the prerequisite, with no filler. Efficient and readable.

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 output schema, the description must carry return-value meaning, and it does list the returned fields, plus the auth requirement. But it omits the sole parameter's meaning and any response shape details, leaving an agent under-informed for the one configurable input.

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 single parameter 'days' (integer, 1-90) has 0% schema description coverage and the description never mentions it. 'Daily usage' gestures at day granularity but does not explain what the days parameter controls, so the gap is unfilled.

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 names a specific resource and enumerates the returned data: daily usage, remaining quota today, and plan limits. That is concrete and distinguishable from siblings like list_plans or whoami, though it doesn't explicitly say what it is not.

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 (query your quota/usage) and the auth prerequisite 'Needs an organization key' is stated, but there is no explicit when-to-use, when-not, or alternative routing versus siblings such as list_plans.

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