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

Annotations already declare readOnlyHint=true and idempotentHint=true, so safety is covered. The description adds useful operational behavior beyond the annotations: a bearer API key must be configured, and the key is issued from a specific signed-in human flow.

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 main purpose is front-loaded, followed by an explicit use case and the required auth setup. The API-key note is lengthy but necessary; no sentences are 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?

Given that there are no parameters, the output schema exists, and annotations cover the safety profile, the description provides sufficient context: what is returned, when to call the tool, and what authentication is required. An agent can decide and invoke it correctly without missing information.

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 input schema has zero parameters, so schema coverage is 100% and there is nothing for the description to add. The baseline for zero-parameter tools is 4.

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 identifies the resource (authenticated account) and what it exposes (credit balance and plan), and gives an explicit usage context ('Check this before a batch of generations'). This makes it stand apart from siblings like estimate_credit_cost or generate_video, which target cost estimation and generation.

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?

It states a clear trigger — check before a batch of generations — and mentions the API-key prerequisite. It does not name alternative tools or when-not conditions, so it falls slightly short of a 5.

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