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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds two pieces of context annotations cannot express: the balance is denominated in cents (unit conversion required) and the call is free, which matters in a credit-metered API. It does not describe the rest of the account payload, but the added value beyond annotations is real.

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?

Two short fragments, front-loaded with the returned resource and followed by the cost note. Every element (resource, unit, cost) earns its place and nothing is padded.

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?

There is no output schema, so the description carries the burden of describing the return value; it does so at a summary level (account identity + prepaid balance in cents). For a trivial, zero-argument self-lookup this is nearly sufficient, though the exact account fields returned are not enumerated.

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 takes zero parameters, so there is nothing for the description to disambiguate; the baseline for a 0-param schema is 4. No misleading invocation hints are present.

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: the calling account plus its current prepaid balance, with the unit (cents) stated. It is clearly distinct from every sibling, all of which return suburb/property/economics data. It lacks an explicit verb (e.g. 'Returns'), but the intent is unambiguous.

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?

Usage is only implied: an agent infers this is the tool to check remaining credit before spending it on paid calls. The '**Free.**' note gives useful context that calling this costs nothing, but there is no explicit when-to-use or when-not-to-use guidance and no named alternative.

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