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

Beyond the annotations, the description discloses concrete state effects: an invoice is created, order_line.qty_invoiced increases, and order.status moves to closed when fully billed. It also identifies the due-date source and warns against overriding it, which is exactly the kind of mutation context 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?

The description is front-loaded with the core action and billing rule, then gives the due-date constraint and effects. It is appropriately sized for a financial mutation and every sentence contributes useful context.

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 one-parameter mutation with no output schema, the description covers the key billing rule, due-date behavior, and side effects. It could be slightly more complete by stating what happens when there is nothing shipped or unbilled, but the core invocation context is present.

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 order_id is already documented as the existing order to bill. The description adds business context about shipped/unbilled scope, but it does not add syntax or deeper parameter-level meaning beyond 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?

The description states a specific verb and resource: issue an invoice for everything shipped on an order and not yet billed. It also distinguishes the billing rule from billing ordered quantities, so an agent can tell this is the shipment-based invoicing action rather than a generic invoice creator.

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?

It clearly explains the usage context: bill shipped-but-unbilled order lines, and do not pass a due date because terms govern it. However, it does not explicitly name alternative tools or when-not-to-use conditions, such as what to do before shipment or when to use void/credit-note tools instead.

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