Overdue invoices for a customer

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

Annotations already declare readOnlyHint, idempotentHint and closed-world, so the safety profile is covered; the description adds real value by disclosing that aggregation happens in SQL (no client-side summing or pagination caveats) and that the response carries an outstanding total. It does not state what happens if the customer fails to resolve, which is the one behavioral gap.

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?

Three sentences, front-loaded with what is returned and under which conditions, with the usage hint last. 'Aggregation is done in SQL' is a mild implementation detail but does convey that totals are precomputed rather than left to the caller.

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 two-parameter read with no output schema, the description covers the filter semantics and signals the aggregate field, which is enough for correct invocation. It leaves the per-invoice return shape unstated, which is acceptable given the tool's narrow purpose.

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 both parameters are already documented, including the date pattern and the 'must resolve to a real customer' constraint. The description only restates 'as of a given date' and 'one customer' without adding format or failure semantics, so baseline 3 applies.

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 and resource ('Returns every invoice for one customer') plus precise scope qualifiers: past due date, not fully paid, as of a given date. The scope is distinguishable from getPaymentHistory or getReceivablesAging in substance, but the description never names or contrasts those siblings.

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?

'Use this for any question about what a customer owes' gives a usage context but is over-broad: it plausibly overlaps with getReceivablesAging, which also concerns outstanding balances, and no exclusion or alternative routing is offered. Usage is implied rather than delimited.

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