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

readOnlyHint=true already tells the agent this is a safe read. The description adds useful context beyond that — the unit of measure (US cents) and the fact that top-ups are not performed here — but says nothing about behavior for non-prepaid accounts, error cases, or freshness of the value.

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 with zero filler, and the core fact (what the value is, in what unit) is 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?

A zero-parameter read tool with an output schema and readOnly annotation needs little prose, and the description covers the essentials (unit, source of top-ups). A brief note on behavior when no prepaid balance exists would make it fully complete.

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 the baseline is 4. Nothing about argument semantics needs explaining, and the description correctly spends no space on inputs.

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 concrete resource and value: the account's prepaid balance, with the unit (US cents) specified. It is unambiguous and clearly distinct from the sibling audit tools, though it describes the return value rather than naming the retrieval action explicitly.

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 note that top-ups happen in the Grisoco dashboard implicitly scopes this tool to reading the balance only and signals the excluded operation. No explicit when-to-use clause, but there are no sibling alternatives that could be confused with it.

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