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

Beyond the destructive and non-readonly annotations, it discloses key consequences: FastBill assigns the invoice number and PDF, the invoice becomes uneditable, it can only be canceled afterward, and no customer notification occurs. This is exactly the behavioral context needed for a destructive mutation.

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 warning is front-loaded with 'WRITE, NOT REVERSIBLE', followed by the operational details and confirmation requirement. Every sentence contributes useful context, with no filler.

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 destructive, non-idempotent one-parameter tool with no output schema, the description covers irreversibility, side effects, resulting invoice state, customer notification behavior, and the required user confirmation. Nothing critical for correct invocation is missing.

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?

The schema has 100% description coverage and clearly identifies invoice_id as the FastBill id of the DRAFT invoice. The description reinforces that the target must be a draft, but does not add parameter-level details 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: turning a draft invoice into a final invoice. It clearly distinguishes this operation from invoice creation or payment marking by explaining the draft-to-final transition and FastBill-side consequences.

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 gives a clear precondition: only call after the user has confirmed the draft. It also clarifies that nothing is sent to the customer, but it does not explicitly name sibling alternatives such as creating a new invoice or canceling an existing final invoice.

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