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

The readOnlyHint annotation already signals a safe read operation. The description adds only 'Free', which is a billing note, not behavioral context about return format, rate limits, or authentication. It does not describe what the tool actually returns or any side effects, so it adds minimal value beyond the annotation.

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?

The description is very short and concise, but it is not well-structured—it consists of two fragments rather than a clear sentence. It front-loads 'Storage usage and quota' before 'Free', which is reasonable, but the lack of a verb makes it feel incomplete. It earns a middle score because it is concise but lacks proper sentence structure.

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?

There is no output schema, so the description must explain what the tool returns. It vaguely says 'Storage usage and quota' but does not specify the format, units, or whether it returns both usage and limit. It also does not indicate that it refers to the current user's storage, which could be ambiguous. Given the minimal context, an agent would not know what to expect in the response, making this incomplete.

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 zero parameters, and schema coverage is trivially 100%. With no parameters to explain, the description does not need to add parameter details. The baseline of 4 is appropriate since there is nothing to document.

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 is a fragment ('Storage usage and quota. Free.') rather than a clear verb-resource statement. It implies the tool reports storage usage and quota, but it never explicitly says 'get' or 'retrieve'. The title 'Check storage usage' is clearer, but the description itself is vague. It does distinguish from sibling tools by naming the storage resource, but lacks a specific action verb.

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?

There is no guidance on when to use this tool versus alternatives. It does not mention whether to prefer it over get_credits, get_pricing, or other account-related getters, nor does it state any conditions or context. The only extra note is 'Free', which is a cost attribute, not a usage guideline.

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