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

Annotations already mark it read-only and non-destructive, so the description only needs to add extra context. It discloses that only active credits are returned, that credit/confirmation numbers are deliberately hidden, and that expiration dates are included 'when known'—useful behavioral nuances beyond the annotations.

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?

Four sentences, each earning its place: what the tool returns, the return fields, when to use it, and a key limitation. Information is front-loaded and there is no fluff.

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 with an output schema, the description covers purpose, return content, invocation triggers, and privacy limitations. Nothing an agent needs to call it correctly appears missing.

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 schema coverage is trivially 100%, so the baseline for parameter semantics is 4. The description correctly focuses on behavior and return data rather than parameters, needing no additional compensating detail.

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 names a specific resource ('airline flight credits, eCredits, travel funds, vouchers, and travel-bank balances') with a clear verb ('Get'), and lists the returned fields. It implicitly distinguishes itself from the sibling get_free_night_credits by focusing on airline/travel credits rather than hotel free-night credits.

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 gives explicit guidance: 'Use this whenever the user asks whether they have unused airline money, credits from cancelled flights, or travel vouchers.' This is a clear invocation condition, though it does not mention when not to use it or name an alternative tool.

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