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

Annotations already declare readOnlyHint, idempotentHint, and closed-world scope, so the safety profile is covered. The description adds behavior beyond that: the result ordering ('worst first'), the per-currency aggregation, and the free/no-cost trait, none of which are in the structured fields. It stops short of describing pagination or result size limits, which is the only missing behavioral note.

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 short sentences, front-loaded with the scope and ordering, then the routing alternative and cost note. Every clause carries information; nothing repeats the title.

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's summary of return contents (days overdue, amount, per-currency totals) and sort order carries that burden well. Combined with the tri-state annotations and fully documented single parameter, an agent has everything needed to call and interpret it.

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% and the single as_of parameter is fully documented in the schema, including its default of today. The description adds no meaning beyond that, which is the expected baseline when the schema does the work.

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 ('List every invoice not paid in full whose due date has passed'), plus ordering ('worst first') and payload ('days overdue and the amount, then a total per currency'). It also names the sibling it differs from, so an agent can distinguish it from invoice_list 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?

Explicitly routes the agent: this tool is the filtered past-due view, and 'Use invoice_list for everything still open' names the alternative and the condition that selects it. It also flags 'Free', which is a useful cost signal for tool selection.

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