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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral detail: null semantics for renewsAt/renewalCredits/runsOutAt and the fact that all generation capabilities draw from a single shared balance, which is the key behavior an agent needs to plan spend.

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?

Purpose is front-loaded in the first clause and every subsequent clause carries information (returned fields, shared balance, invocation timing). The first sentence is long and clause-dense, packing balance, available, renewsAt, renewalCredits and runsOutAt into one run-on structure, which slightly hurts scannability.

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?

An output schema exists, so the description is not obligated to enumerate return fields, yet it does so with helpful null-case semantics. Combined with the spend guidance and no-parameter signature, an agent has nearly everything needed; the only gap is relationship to the similar read_points sibling.

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 and the schema is empty with additionalProperties=false, so there is nothing for the description to disambiguate. Per the zero-parameter baseline this sits at 4; the field enumeration describes outputs rather than inputs and so adds no parameter-level value.

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 and resource ('Show the signed-in user's Vidova plan and credits') and enumerates exactly what is returned, including field-level semantics for balance, available, renewsAt, renewalCredits and runsOutAt. An agent can distinguish it from generic sibling readers like read_points without opening either 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 explicit situational guidance: 'Check it before costly work such as a long video or music generation,' and notes that agent/video/images/music/voice/analysis/search/cloud renders all spend from this one balance. It stops short of naming alternatives (e.g. read_points) or stating when not to call it, so it is clear context rather than a full when/when-not rule.

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