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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds context beyond that: results are scoped to the calling API key, the Earn profile may be absent ("if any"), and credit-pack output reflects a live promotion such as Black Friday x2, warning the agent that pricing content is time-sensitive.

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?

It is a single dense sentence, front-loaded with the resource identity before the content list, and every clause describes a distinct returned field rather than padding. It would read better split into a purpose sentence plus a returns list, but no wording is wasted.

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 carries the full burden of explaining return values, and it does so item by item, including volatile and conditional elements (promotions, optional Earn profile). For a zero-parameter read tool with annotations covering the safety profile, nothing an agent needs 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?

The tool takes zero parameters, so there is nothing to document and the baseline of 4 applies. The description correctly implies a no-argument call by framing the account as implicitly derived from the API key.

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 the exact resource ("The CartViral account behind this API key") and enumerates its contents: plan, billing interval, credit balance, per-clip credit prices, plan prices on both intervals, credit packs, and the Earn profile. No sibling tool touches account or pricing data, so an agent can distinguish it from every generate_*/list_* tool without opening a 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?

The closing "Call this first." is an explicit ordering directive that tells the agent when to reach for this tool relative to the generation toolset. It does not name exclusions or a case where this tool should be skipped, so it falls short of full alternatives guidance.

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