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 still adds real value beyond them by explaining that reserved credits are transient and 'the unused part comes back when a video is done', preventing an agent from misreporting reserved credits as spent. It stops short of describing a return format, but the data shape is implied well enough.

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 result is front-loaded: what the tool returns comes first, followed by the reserved-credit nuance and the operational constraint. Every clause earns its place — the parenthetical clarifies a genuinely confusing distinction, and the final sentence prevents a costly misstep.

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 parameterless read tool with annotations and no output schema, the description covers what it does, the meaning of the two returned values, the read-only nature, and the boundary against purchasing behavior. Nothing an agent needs to call it correctly 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 for the description to disambiguate and the baseline of 4 applies. The description adds no parameter detail because none is needed.

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 (ClipFlux credits) and the two specific quantities returned: spendable credits and credits reserved for in-progress videos. It even clarifies the semantics of 'reserved' versus 'spent', so an agent knows precisely what this tool reports. No sibling in the list exposes credit balances, and the description makes that scope unmistakable.

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 establishes clear context ('Read only') and an explicit exclusion: 'Plans and credits are managed on clipflux.ai; never offer to buy any.' That tells the agent not to attempt purchasing or plan changes through this tool, which is valuable routing guidance. It does not explicitly name an alternative tool for credit-related actions, but no such sibling exists.

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