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

Annotations already establish a safe read (readOnlyHint=true, destructiveHint=false), and the description adds genuinely useful behavior: page size of 100 and cursor-based pagination, overdue/due-date semantics, and an explicit auth requirement ('Cotlet API key with access to this app'). This is well beyond what the annotations convey.

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?

The content is dense and mostly front-loaded, leading with the resource and returned fields before the filters. There is mild redundancy ('newest first' appears twice) and the opening sentence is a little muddled, but no sentence 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?

With no output schema, the description carries the burden of describing returns, and it does list the key fields plus pagination and auth behavior. An agent has enough to call it correctly; only the ambiguity around days_overdue keeps it from being fully complete.

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 3 is the baseline, but the description adds real meaning: overdue is computed against the invoice due date or the Partial/Deposit amount due date, invoices without a due date are due immediately, and status values can be comma-combined. Minor noise: it mentions 'days_overdue' which is not one of the 8 parameters, slightly blurring whether it is an input or a returned field.

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 'Lists invoices' plus scope ('of one company') and enumerates returned fields (client, status, dates, amount, balance), so the agent knows exactly what it gets. It stops short of naming sibling alternatives like get_invoice for single-invoice lookup, so it does not achieve full sibling differentiation.

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?

Usage is implied through the filter explanations (status combinations, overdue, date ranges), which guides how to narrow results. However there is no explicit when-to-use-this-vs-alternative guidance, e.g. no pointer to get_invoice for one invoice or list_quotes for quotes.

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