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

Annotations already cover the safety profile (readOnlyHint, destructiveHint=false, openWorldHint), yet the description adds substantial context beyond them: deterministic newest-first ordering, a 100-record page cap, cursor round-tripping, and an explicit auth requirement (Cotlet API key with app access). These are exactly the operational facts an agent needs.

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?

Dense, front-loaded and free of filler, but 'newest first' appears twice in the first two sentences, which is a small redundancy. Length is appropriate for eight filters plus pagination and currency conventions.

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?

There is no output schema, so the description carries the return-value burden and does so: it names total, amount paid, amount due and dunning status, and clarifies the smallest-currency-unit convention with a worked example. Combined with the auth and pagination notes, nothing needed to call it correctly is missing.

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 baseline is 3, but the description meaningfully enriches two params: it interprets the status filter domain (overdue = payment_due OR not_paid, so send both) and explains that cursor is a next_cursor from a prior call with page size <= 100. Other params (date_after/date_before, customer_id, subscription_id) are left to the schema.

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) plus resource (Chargebee invoices) and enumerates the filter dimensions (customer, subscription, status, date) and sort order. An agent can tell this apart from chargebee_get_invoice (single record) and chargebee_list_subscriptions without opening any 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?

Gives concrete operational guidance: pass both payment_due and not_paid to find overdue invoices, and use cursor for pagination. It does not explicitly name the sibling alternatives (e.g. get_invoice for a single invoice), so the when-not-to-use case is left implicit.

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