Get usage & credits

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

The annotation readOnlyHint already communicates that this is a safe read operation. The description adds 'Free' and specifies the output areas (plan, credits, cost estimates), but it does not disclose deeper behavior such as response format or rate limits. This is acceptable for a simple read-only tool, but it does not go beyond annotations significantly.

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 sentence that front-loads the action and delivers all necessary information with no wasted words. 'Free' is an extra useful trait that justifies its place.

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, read-only tool without an output schema, the description covers the core information: what the tool returns (plan, credits, per-action cost estimates). It does not explain the return format, but that is less critical here. A minor gap is the lack of differentiation from get_usage_history, but the tool's simplicity keeps it complete enough.

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 zero parameters, and the schema covers 100% of the parameter space (an empty object). The description adds no parameter-level detail, but none is needed. The baseline for zero parameters is 4.

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 ('Show') and clearly identifies the resource: current plan, credits remaining, and per-action cost estimates. It also implicitly distinguishes itself from the sibling get_usage_history by focusing on current usage rather than historical data.

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 provides clear context for when to use this tool (checking current usage and credits), but it does not explicitly mention alternatives or exclusions. Since the sibling get_usage_history exists, a brief 'for history, see get_usage_history' would have earned a 5, but the current wording is still clear enough.

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