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

readOnlyHint already declares this a safe read, and the description adds substantive behavior the annotations cannot convey: only the FIRST page is returned and there is no continuation endpoint, so truncation is a real risk. That is exactly the kind of hidden limitation an agent needs before calling.

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?

Two dense sentences with the scope, the pagination caveat, and the endpoint all front-loaded; little waste. The raw POST path is mildly implementation-flavored but not harmful.

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 return-shape burden and does name the key returned concepts (unpaid amount, overdue flag, has_more). For a read-only report with a fully documented schema, nothing essential is missing, though the customer-vs-debts-report distinction is not resolved.

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 the baseline is 3, but the description adds meaning beyond the terse schema text: customer_name and customer_id are framed as alternative ways to identify one customer, and period_start/period_end are described as the bounding period. Currency is left to the schema alone.

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+resource+scope: customer invoices with unpaid amount and overdue flag for a period and a single customer. An agent can distinguish it from list-style siblings, though it never names merit_customer_debts_report or merit_sales_report, which cover adjacent territory.

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 real operational guidance — single-customer scope, and that when has_more is true the agent should narrow the period or customer because continuation is unsupported. However it offers no explicit when-to-use-vs-alternatives routing against the overlapping report siblings, leaving that inference to the agent.

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