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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. However, the description adds nothing beyond them — no note about result ordering, pagination, or whether all invoices are returned by default — leaving it as a pure restatement of the title.

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 front-loaded sentence with zero waste. It is appropriately tight, though its brevity borders on under-specification rather than genuine economy.

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 read-only list tool with full schema coverage and an annotations-declared safety profile, the description is minimally adequate. It omits ordering and pagination notes that would help an agent interpret results, and there is no output schema to compensate.

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?

Schema description coverage is 100%, so the single `limit` parameter (default 25) is fully documented in the schema. The description adds no extra meaning, which makes the baseline of 3 appropriate for a one-parameter tool where the schema does all the work.

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 a specific verb (List) and resource (billing invoices), which is unambiguous. It doesn't need to distinguish itself from siblings since none of the surrounding tools deal with invoices, but it also makes no effort to differentiate or scope beyond the bare resource.

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 adjacent ones (e.g., list_reports, list_audits), nor any mention of prerequisites, filters, or pagination behavior. Usage is only implied by the tool name itself.

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