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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: it specifies the time window ('this calendar month') and explains the null limit semantics ('Null limit means the plan is uncapped'). This helps the agent interpret the data correctly, though it doesn't describe response structure—but the output schema is empty, so no additional detail is expected.

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 with no redundancy. The main information (what it returns) is front-loaded, and the second sentence adds an important edge-case clarification. Every word earns its place—no fluff or repetition.

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-parameter, read-only tool with an empty output schema, the description is complete. It states the time period, the metric (course views), the comparison to allowance, and the excess cost rate. It also handles the null limit edge case. An agent knows exactly what to expect and how to interpret the result.

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 no parameters, so the description doesn't need to explain any. Per the baseline for zero parameters, a score of 4 is appropriate since the description provides relevant context (what data is returned) but doesn't need to add parameter-specific semantics. It correctly avoids inventing parameters.

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 states what the tool does: returns the current calendar month's course views against the plan's allowance and any excess cost at the published rate. It distinguishes itself from other get_* tools by specifying the exact resource (plan usage) and the specific metrics (views, allowance, excess cost). The 'null limit' clarification adds precision.

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?

The description implicitly indicates when to use it—whenever you need plan usage for the current month. It provides clear context (this calendar month, course views, excess cost) but does not explicitly mention alternatives or when not to use it. Since it's a get_* for usage, the purpose is obvious, but explicit exclusions would elevate it.

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