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

Annotations already declare the read-only safety profile, but the description meaningfully adds behavior: results are ordered newest first, status is computed live (a sent invoice past due reads as overdue), and totals outstanding/overdue are returned. These are real behavioral traits not derivable from the annotations.

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 that front-loads what is returned and packs ordering, computed status, and totals without a wasted word.

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 no output schema, the description does the work of explaining the return payload (invoices, live status, outstanding/overdue totals), and annotations cover safety. It omits pagination/limit behavior and the per-invoice field list, leaving a minor gap for a simple read tool.

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 50%: the status enum is explained in the schema, but limit is undocumented anywhere. The description adds conceptual clarity around 'overdue' and 'live status' that touches the status filter, but it never addresses limit or the parameter surface directly, so it neither compensates fully nor ignores the schema.

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 names the specific resource (the signed-in person's invoices) and implies the list verb clearly with scope ('newest first'). It is obviously distinct from create_invoice, send_invoice, and mark_invoice_paid, but it does not explicitly name or contrast with those siblings.

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 explicit when-to-use guidance or any mention of alternatives such as mark_invoice_paid or send_invoice. Usage is only inferable from the resource name; nothing tells the agent when this is the right choice over other invoice tools.

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