Set the note printed on a customer's invoices (write)

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

With no annotations provided, the description carries the full disclosure burden. It clearly flags the operation as WRITE, states that it is a partial update affecting only the note, and explicitly notes that previously issued invoices are never modified. It omits details like error behavior or permissions, but the key side effects are disclosed.

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 tight sentences that front-load the operation type and core behavior, then add use cases and temporal scope. Every sentence earns its place with no filler or redundancy.

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 write tool with no output schema, the description covers what is changed, what is not changed, when it takes effect, and typical use cases. An agent has enough information to select and invoke it correctly.

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 baseline is 3. The description adds useful semantics for the 'note' parameter by giving concrete examples of what belongs there, while the schema's own note description already explains the partial-update behavior. This goes just beyond the structured fields.

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 opens with a specific verb and resource: 'Sets the note printed at the bottom of every upcoming invoice of a ProAbono customer.' It also differentiates itself from sibling payment-settings tools by clarifying it 'changes nothing else about their payment settings.'

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?

The description gives concrete intended uses (purchase order number, cost centre, customer accounting needs) and a clear temporal boundary: applies to future invoices only, never already issued ones. It does not explicitly name sibling alternatives like set_payment_method or set_next_billing_date, but the scope phrasing makes the appropriate use case clear.

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