balance

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

The description adds no behavioral traits beyond the annotations, which already declare readOnlyHint, idempotentHint, and destructiveHint false. No additional context about rate limits, authentication, or side effects is provided.

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 a single concise sentence that directly conveys the tool's purpose without any filler or redundancy.

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 simple nature of the tool, the presence of an output schema, and annotations indicating a safe read-only operation, the description is largely complete. It could slightly benefit from an explicit verb, but the overall context is sufficient.

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 input schema fully documents the single parameter 'api_key' with a description. The tool description adds nothing about parameters, but with 100% schema coverage, the baseline of 3 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 clearly states what the tool provides: remaining free calls and prepaid credit balance. It identifies a specific resource and differentiates from the sibling verification/receipt tools, though it lacks an explicit verb like 'check' or 'get'.

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?

No guidance is given regarding when to use this tool versus alternatives. The description simply states what the balance is, without mentioning any context for use or excluding other scenarios.

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