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

Annotations already declare this a safe, read-only, closed-world operation, so the bar is low. The description still adds genuine value beyond them: the receiving number is returned masked, and 300 points converts to roughly one minute of calling, which tells the agent how to interpret the balance without a follow-up call.

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?

Three short sentences with no filler, front-loaded on the returned fields before the sibling routing. The first sentence is a bare noun-phrase list with awkward line wrapping, but nothing is wasted.

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 an output schema present, the description is not obliged to document return values, yet it still names the key fields and their units. Combined with the sibling cross-references, an agent has everything needed to select and interpret this tool correctly.

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 description to disambiguate and the baseline of 4 applies. No parameter-level guidance is needed or missing.

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 enumerates exactly what the tool surfaces: points balance, display name, and the selected masked receiving number for call_me. The verb comes from the title ("Check account status") rather than the body, but the resource set is specific enough to distinguish it from siblings like caller_id_status and receiving_phone_status.

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 explicitly routes the agent to receiving_phone_status for setup and caller_id_status for outbound display state, which are concrete alternative-selection rules. It stops short of stating the primary when-to-use condition (checking balance/account identity) in so many words, leaving that to inference from the listed return values.

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