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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered; 'read-only' largely repeats the annotation. The one genuinely additive detail is that the call is free, plus the disclosure of what data is exposed (credits breakdown, cancel flag). Adequate but not rich beyond structured fields.

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 resource and its returned fields, followed by the usage trigger. The field enumeration is dense but each item is meaningful; no filler sentences.

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 and no parameters, the description carries the burden of telling the agent what comes back, and it does so by listing the concrete fields (plan, cycle, credit buckets, extraction usage, renewal, cancel status). Only minor gaps remain, such as nothing about error or empty-account behavior.

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 takes zero parameters, so the baseline is 4; there is nothing for the description to disambiguate and schema coverage is trivially complete.

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?

States a specific verb ('Show') and resource ('the account's ScriptGrain subscription') and enumerates exactly what is returned: plan, billing cycle, status, credits, extraction usage, renewal, cancel flag. An agent can distinguish it from list_generations, get_invoice, or upgrade_plan without opening any schema.

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 two concrete triggers: when a generation was refused for credits, and before suggesting an upgrade. The latter implicitly routes the agent toward upgrade_plan, but no alternative is named explicitly, so it falls just short of a full when/when-not statement.

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