Get your credit balance and usage

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

Annotations already declare read-only, idempotent, non-destructive, so the safety profile is covered; the description still adds a non-obvious fact beyond them — that the call consumes no credits, which matters for an agent operating under a budget. It does not describe units, currency, or how many 'recent' entries are returned.

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 sentences, zero filler, with the capability stated first and the no-cost guarantee second — exactly the information an agent needs, front-loaded.

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 no output schema, the description adequately previews the return content (balance, recent charges, top-ups). It stops short of stating response shape, currency, or recency window, which an agent might want given there is no output schema.

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, which is the baseline-4 case; there is nothing for the description to disambiguate. Schema coverage is 100% and the empty object confirms no arguments are needed.

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?

States a specific verb+resource (get credit balance) and scopes the result set (most recent charges and top-ups), which is more precise than the title alone. No sibling tool covers billing/usage, so no differentiation is needed, but it also doesn't explicitly claim that territory against the rest of the catalog.

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?

'Read-only; no credit used' implicitly tells the agent this is always safe to call, but there is no explicit when-to-use or when-not guidance, nor any mention of alternatives (none of the siblings overlap, so the gap is small). Usage is inferred rather than stated.

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