Vision API credit balance

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

The description adds valuable behavioral details beyond the readOnlyHint annotation: it is free (consumes no credits), and it explains the order of bucket spending. This gives the agent a deeper understanding of what to expect.

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 concise and front-loaded with the main purpose. Each sentence adds unique information: the resource, the cost, the usage scenario, and the bucket order. No unnecessary words.

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 the tool's simplicity (no parameters), the existing annotations, and the presence of an output schema, the description fully covers the tool's context. It explains when and why to use it, and the cost implication.

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 has no input parameters, so the description has nothing to add. Per the rubric, 0 params gets a baseline of 4; no further clarification 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 clearly identifies the tool as providing the account's credit balance and per-bucket breakdown, which is distinct from sibling tools focused on presets and analysis. The 'Worth checking before a large batch' phrasing reinforces its purpose as a balance check.

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 explicitly states when to use the tool ('before a large batch') and explains the benefit (avoiding insufficient_credits errors). It also provides the bucket consumption order, giving the agent a clear usage context.

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