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

No annotations are provided, so the description carries the full burden. It discloses the return content (invoices with totals, paid, balance, total owed), which is useful behavioral context since there is no output schema. However, it omits whether the operation is read-only (implicitly yes), permission requirements, time-range scope, or pagination behavior.

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?

A single well-formed sentence with no filler. The key output content is front-loaded and every phrase adds meaning.

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 simple one-parameter read tool with no output schema and no annotations, the description adequately explains what data is returned. It could be more complete by specifying that only a customer_id is required and mentioning any scope limitations (e.g., date range or pagination), but the core information an agent needs to invoke it is present.

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 sole parameter customer_id has 0% schema description coverage, and the description only implies it through the possessive 'a customer's account statement'. It does not state the expected format (UUID), whether the ID is required, or how to obtain it, so the description fails to compensate for the schema gap.

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 clearly states the resource (a customer's account statement) and enumerates its contents: every invoice with total, paid, balance, and the total owed. It does not explicitly differentiate this from sibling tools like invoices_aging or reports_owed, but the per-customer statement framing is specific enough for an agent to understand the tool.

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 use this tool versus alternatives such as invoices_aging, reports_owed, or fees_statement. The description only defines what the tool returns, leaving the agent to infer usage context.

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