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

With no annotations, the description carries the full burden. It discloses the auth requirement ('Requires: token') and the meaningful behavioral linkage that order_vps draws down this balance automatically, which is genuinely useful context. It stops short of stating the return shape or any rate/pagination behavior, so it is adequate but not rich.

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 tightly written sentences with zero filler, front-loading what is returned before the dependency and auth note. Every clause earns its place.

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 with no output schema, the description covers what is returned (balance and currency), the auth requirement, and the cross-tool dependency. The only minor gap is that the exact return shape isn't specified, but this is a low-complexity tool where that omission is acceptable.

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 schema to document and no parameter semantics to add. Baseline 4 applies; no description compensation is 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 and resource: 'Return the account's prepaid credit balance and currency.' An agent can immediately tell this is a read of the balance, distinct from the write-oriented sibling topup_balance, without opening any schema.

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?

It gives useful relational context by noting that `order_vps` spends from this balance automatically when sufficient, which hints at why an agent would check it. However, it never states explicit when-to-use/when-not conditions or names alternatives such as topup_balance, leaving usage largely implied.

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