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

The readOnlyHint already establishes that this is a safe read operation. The description adds useful behavioral context beyond annotations, specifically the Payments-area key requirement and the optional inclusion of upcoming scheduled subscription invoices, though it does not describe pagination or return format.

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 compact and front-loaded, stating the core operation first, then the optional behavior, prerequisite, and endpoint. Every element adds useful information without repetition.

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 simple two-parameter read-only list operation with complete schema descriptions and a readOnly annotation, the description gives enough context to select and invoke the tool. It could be richer about return shape or pagination since no output schema exists, but the essential 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 the schema already documents both parameters. The description adds meaning by explaining that include_scheduled relates to upcoming subscription invoices and that this option requires a Payments-area key, which is not present in 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: 'List the invoices of one order.' It also clarifies the optional scope for scheduled subscription invoices and gives the exact Admin API endpoint, letting an agent distinguish this from payment-history tools such as get_order_payments.

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 provides clear usage context for listing invoices tied to a single order and notes the Payments-area key prerequisite for scheduled invoices. It does not explicitly name alternatives or when not to use this tool, so it falls short of full when/when-not guidance.

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