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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description should then tell the agent what the snapshot contains (per-tool granularity? current period? account identity?) but gives only a loose field list plus the cryptic "Free.", which adds almost no behavioral context.

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?

Brevity is appropriate for a no-argument read tool, and the returned data is front-loaded. However, the one-word sentence "Free." is unexplained and reads as noise rather than earning 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?

With no output schema, the description must explain return values; it names three of them but omits the shape and meaning of "plan" and "price of each tool" (currency, per-call vs per-unit). Adequate for a simple read but leaves an agent guessing about what it will receive.

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 no parameter information the description needs to supply. The baseline of 4 applies; nothing is misleading here.

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 states what the tool surfaces (plan, remaining credits, per-tool price) but as a noun fragment with no verb and no statement that it returns the caller's own account. The trailing "Free." is ambiguous — it could be a plan tier or a claim that the call costs nothing.

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?

There is no guidance on when to call this versus the many sibling tools. A reader can infer it should be checked before running cost-incurring operations, but that inference is never stated, and no preconditions or alternatives are named.

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