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

With no annotations, the description carries the full burden. The phrasing 'Check' and 'Shows' implies a read-only operation, and the top-up URL provides useful context. However, it does not disclose whether the balance is real-time, cached, or whether authentication is required, leaving some behavioral unknowns.

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 two sentences, front-loaded with the primary action, and every word adds value. It avoids fluff and stays well within appropriate size.

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 simple 0-parameter tool with no annotations and no output schema, the description covers the core functionality, the meaning of the balance, and the follow-up action to top up. It lacks explicit return format or refresh semantics, but these are minor for a balance check 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?

The tool has zero parameters, so the baseline is 4. The description adds meaning by explaining that the balance represents 'available credits for running services', which gives semantic context beyond the empty parameter schema.

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 names the exact resource 'XPay wallet balance', clearly distinguishing it from sibling tools like xpay_details and xpay_discover. The added context 'Shows available credits for running services' further clarifies the tool's purpose.

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 context by stating it shows available credits for running services and suggests topping up if balance is low, but it does not explicitly mention when to use this tool versus alternatives like xpay_details or xpay_run. No exclusion criteria are provided.

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