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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds that the balance is tied to the API key's account and that calls are free, which is useful behavioral context, but it does not mention rate limits, response shape, or freshness of the balance.

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 two short sentences and is front-loaded with the core result: credits remaining. The second sentence adds a useful behavioral note without waste.

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 simple zero-parameter read-only balance check with no output schema, the description is mostly complete: it identifies the account scope, the value returned conceptually, and the cost of calling. It could say more about the response format or unit, but nothing critical is missing for correct invocation.

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?

This tool has zero parameters, so there is no parameter semantics burden on the description. The baseline for zero-parameter tools is 4, and the description does not create confusion about inputs.

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 states a specific resource and scope: the credits left on the Movoa account behind the caller's API key. That is clear enough to distinguish it from check_status and generate_video, but it does not explicitly name or differentiate against those siblings.

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 says the tool is 'Free to call,' which is useful context, but gives no guidance on when to use this tool versus check_status or other sibling tools. There are no when-to-use, when-not-to-use, or prerequisite statements.

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