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

With no annotations, the description carries the full burden and largely does: it discloses the auth prerequisite ('[KEY REQUIRED]'), that the call is a read-only status check, and what comes back. It leaves one relevant behavior unspecified — whether this call itself consumes credits or is free — which matters for a credit-checking tool.

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?

Front-loaded with the key requirement and the core purpose, with the call-to-action last. The Korean and English versions are parallel duplicates, which roughly doubles length, though the i18n duplication is defensible and each sentence still carries content.

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-param, no-output-schema tool with no annotations, the description supplies the prerequisite, the return fields, and the decision context for calling it. The only material omission is whether the call is itself metered.

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. The description correctly adds no parameter discussion and instead covers return content, which is the right use of space.

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 ('account status for the API key in use') and enumerates the payload — remaining credits, plan, top-up link — which is more than the name implies. It does not name a sibling (e.g. get_pricing) as the alternative for top-up, so it stops short of full disambiguation.

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?

Gives an explicit trigger condition: call before a long run of metered queries to avoid an exhausted balance mid-task. That is actionable when-to-use guidance. It does not state when not to call, nor does it name an alternative tool for pricing/purchase.

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