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

With no annotations provided, the description carries the full burden. It implies a safe read-only balance check ('has left', 'checking before booking'), ties the balance to the API key holder, and adds useful policy context that unpaid renders are refused. It does not explicitly say 'read-only' or 'does not consume credits,' but the wording strongly conveys that.

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?

Two sentences, both purposeful: the first states the tool's result, the second gives a concrete, decision-relevant use case. There is no fluff or redundant wording.

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 zero-parameter balance getter, the description is nearly complete: it identifies the resource, the owner, and when to call it. It does not spell out the exact return format or error behavior for an invalid API key, but that is a minor gap given the simplicity of the tool.

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?

There are zero parameters, so there is no parameter documentation burden. The description adds no parameter information, but none is needed; baseline 4 for zero-parameter tools is appropriate.

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 exactly what the tool returns: how many ViewMax Studio credits the API key holder has left. It clearly scopes to the API key holder and the ViewMax Studio credit resource, and it is unmistakably distinct from the video-generation siblings (generate_video, get_video, list_video_models).

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 gives an explicit trigger: worth checking before booking an expensive render, plus the consequence that an unpaid render is refused outright. It does not name alternatives or exclusions, but the sibling tools are unrelated, so no exclusion guidance is really needed.

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