Unpaid invoices

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds real behavioral detail beyond them: result ordering (oldest due date first), fixed page size of 50, and the non-obvious fact that `total` and `total_due` aggregate across all pages rather than the current page.

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?

Two sentences, zero filler. Core selection semantics come first, then the pagination protocol, with the cross-page totals caveat folded in where it matters.

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?

A read-only paged list with an output schema, 100% parameter coverage, and a description that covers filtering, ordering, page size, and pagination continuation. An agent has everything needed to call it and to keep paging 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?

Schema coverage is 100% and each parameter already carries its own description, including `days` defaulting to 30 and `cursor` being the previous `next_cursor`. The description's wording ('more than `days` days after their due date') clarifies the comparison is strict and past-due relative, but otherwise restates the schema, so the baseline 3 applies.

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?

States a specific verb and resource ('list the invoices still unpaid') plus precise scoping rules: more than `days` past due, evaluated at `as_of`, oldest due date first, 50 per page. An agent knows exactly what set of records this returns and in what order.

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?

The filter semantics make the usage condition explicit (invoices unpaid beyond a past-due threshold at a given date), and the pagination rule names the exact trigger (`next_cursor` present → call again with it). No when-not guidance or named alternatives are given, but no relevant sibling exists in this catalog.

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