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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so safety is covered structurally. The description adds one genuinely new behavioral fact — results come back newest first — but says nothing about scoping (all tenants? all invoices?) or rate/volume 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 front-loaded sentence with zero filler. It is arguably too terse for the tool's pagination quirks, but nothing written is wasted.

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 zero-required-param read-only list with full schema documentation and complete annotations, most of what an agent needs is present. The gaps are real though: no statement of which invoice items are returned (all rows? tenant-scoped?) and no mention that a row's contents are undocumented, which matters since there is no output schema.

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% and the schema itself explains the unusual dual response shape (bare array vs {items, next_cursor, limit}) in detail. The description adds nothing about limit or cursor, so the baseline of 3 applies — the schema does all the work here.

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 ('List') and resource ('invoice_item rows') plus the ordering ('newest first'), so the agent knows this is a read/list operation over invoice line items. It does not explicitly distinguish itself from invoice_item_read or invoice_list, but the list/read split is inferable from the name alone.

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 versus invoice_item_read (single row), invoice_list (invoices), or quote_item_list. The agent must infer usage entirely from the name and schema; no exclusions or alternatives are mentioned.

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