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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful behavior beyond that: pagination mechanics ('Pages hold 1 to 100 invoices; pass next_cursor back as cursor'), default sort order (newest first), and an auth requirement ('the user's Cotlet API key with access to this app'). This is meaningful extra context, though return shape specifics remain thin.

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?

Front-loads the resource and fields, then layers use case, pagination and auth. Mostly efficient, but the lead fragment duplicates the same information ('number, supplier, amounts and due date, newest first' then 'with the supplier, the date, the due date and the total'). Minor redundancy keeps it from a 5.

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 carries the return-value burden and does partially discharge it by naming the fields returned. Pagination, sort order and the API key prerequisite are all disclosed, covering what an agent needs to invoke it correctly. It lacks detail on error/permission behavior and exact return structure.

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%, so the schema already documents limit, cursor, date_from, date_to and supplier_id. The description reinforces the limit range and cursor reuse but adds no syntax or semantics beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 and resource ('Lists the supplier invoices in Pennylane') and enumerates the returned fields (number, supplier, amounts, due date). An agent can distinguish this supplier-facing list from the sibling pennylane_list_customer_invoices, though the distinction is only implicit via 'supplier'. The purpose is unambiguous but not sharpened against siblings the way a 5 would require.

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?

Provides a concrete use case that ties directly to a sibling: 'Use it to check whether a PDF was already imported before you import it again', routing the agent to pennylane_import_supplier_invoice. No explicit when-not or alternatives among the other list tools are given, so it stops short of a 5.

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