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

With no annotations, the description carries the burden of safety disclosure. 'Check' strongly implies a read-only operation, but it does not explicitly state that there are no side effects, permissions needed, or rate limits. This is acceptable but not fully transparent.

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 conveys the essential function with no redundancy. It is front-loaded with the action ('Check') and directly states the target, making it highly efficient.

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 low complexity, no parameters, and no output schema, the description adequately explains the purpose. It could optionally mention the expected return format (e.g., numeric balance, currency), but this is not critical for a simple balance check and the description is otherwise complete.

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 has zero parameters, so the description does not need to explain any. Per the baseline for zero-parameter tools, a score of 4 is appropriate; the description adds no parameter details but none are required.

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 uses a specific verb ('Check') and clearly identifies the resource ('balance of your prepaid credit token'). This unambiguously distinguishes it from siblings like 'get_trial_credit' by specifying 'prepaid credit token.'

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?

The description implies usage by stating the action, but provides no explicit guidance on when to use this tool versus alternatives, nor any exclusions or prerequisites. For a simple read tool, the context is implied but not explicitly framed.

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