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

Annotations already declare read-only, non-destructive, open-world behavior, so the safety profile is covered. The description adds meaningful context beyond that: results are ordered newest first, drafts are unbooked/editable, and a Cotlet API key with app access is required.

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?

Reasonably sized and front-loaded with purpose, but slightly repetitive: the customer/date/line-count/totals list appears twice ('with customer, date, line count and totals' then 'shows its customer, date, number of lines and totals').

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?

No output schema exists, so the description usefully sketches the return shape (customer, date, line count, totals, ordering). Combined with the auth note and the annotation-backed safety profile, an agent has enough to call this correctly, though it omits pagination behavior.

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%, so limit, cursor, and customer_number are already documented in the schema. The description mentions customer and totals but adds no filtering or pagination syntax beyond what the schema provides, 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 clear verb+resource ('List draft invoices') and specifies the scope ('draft invoices that are not booked yet'), which separates it from list_unpaid_invoices and create_draft_invoice. It is clear but does not explicitly name a sibling it should be chosen over.

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 phrase 'not booked yet' and 'Drafts are still editable' implies when this list is appropriate, but no explicit when-to-use/when-not guidance or named alternative is given. Usage is inferable rather than spelled out.

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