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

Annotations already cover the safety profile (readOnly, non-destructive, openWorld), and the description adds substantial context on top: result ordering (oldest due date first), what statuses are never returned, how Partly paid rows display the open amount, page size cap of 200, and the Cotlet API key auth requirement. That is well beyond what structured fields provide.

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-loaded with the filtering scope and efficient overall, but the Sent/Partly paid status list is repeated verbatim in the first two sentences, which is wasted space. Removing that duplication would tighten an otherwise well-organized description.

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 read-only list tool with no output schema, the description adequately covers returns, ordering, exclusion rules, partial-payment display, pagination, and auth. Only minor gaps remain, such as partner_id linkage, which the schema itself partially handles via the list_partners reference.

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 limit, cursor, due_before, and partner_id are already documented in the schema. The description reinforces due_before and adds page-size context ('Pages hold up to 200') but does not clarify partner_id or cursor semantics beyond what the schema states, landing at the baseline.

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?

Specific verb+resource ('list unpaid sales invoices') with the key scope terms defined inline: only Sent or Partly paid qualify, and Paid/Marked paid are explicitly excluded. An agent can distinguish this from the generic list_sales_invoices sibling without opening either schema.

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?

States the inclusion/exclusion conditions and directs the agent to pass due_before for overdue-only views, giving clear context for when to reach for this tool. It does not explicitly name the alternative (list_sales_invoices) for the opposite case, so it stops short of full routing guidance.

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