list_invoices

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

Annotations already declare readOnlyHint=true, so mutation-safety is covered. The description adds beyond the annotation by disclosing permission-based scoping and the invoice contents (storage, API call, data transfer costs). It does not describe pagination, sorting, or response format, but the annotation lowers the bar.

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?

Single sentence with a clear verb and resource upfront and no filler. Every phrase adds information: list scope, permissions, and cost categories.

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?

The tool is relatively complex (12 optional filters, no required parameters, no output schema), and the description covers only the broad purpose and cost contents. Pagination behavior and any default or fallback semantics are left to the schema's page/size documentation, and the output shape is unspecified. Still, the schema covers all inputs and the readOnly annotation covers safety, making it minimally workable.

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?

All 12 parameters have schema descriptions (100% coverage), so the baseline is 3. The description adds no parameter-specific semantics beyond the schema, and the cost-type list relates to the return value rather than inputs. The schema already documents filters and defaults.

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?

Clearly states it lists invoices and scopes them to Sub-Accounts within the caller's permissions, adding the included cost categories. It is easily distinguished from the sibling get_invoice by the list-vs-single contrast, though it does not explicitly name get_invoice as the single-record alternative.

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?

No explicit when-to-use guidance or mention of alternatives such as get_invoice for a single invoice. The only contextual hint is 'within your permissions,' which addresses data scope rather than choosing among tools. The agent is left to infer usage from the tool name and sibling list.

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