Cancel an unpaid invoice and preserve the record with a reason to maintain accurate financial history.
Cancel an invoice that has no payments. The record is kept with the reason.
| Name | Required | Description | Default |
|---|---|---|---|
| reason | Yes | ||
| invoice_number | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: this is a soft void rather than a delete ('the record is kept') and the supplied reason is persisted. It omits whether a void can be reversed or what happens on failure, leaving a small gap.
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 with no filler, and the eligibility constraint is front-loaded before the persistence note. Every sentence contributes distinct information.
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?
With annotations covering the destructive profile and an output schema available for return values, the description only needs to justify the operation and its precondition, which it does. Missing permission requirements and reversibility semantics are minor but real gaps for a destructive operation.
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 description coverage is 0%, so the description must carry parameter meaning. 'The record is kept with the reason' explains why the reason argument matters, but invoice_number is not addressed at all and no format or validation detail is given for either parameter.
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 uses a specific verb and resource ('Cancel an invoice') and adds a distinguishing precondition ('that has no payments') that separates it from sibling tools like mark_invoice_sent or create_invoice. It stops short of explicitly naming an alternative for the case where payments exist, so it is clear but not sibling-differentiated by name.
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 phrase 'that has no payments' gives an explicit eligibility condition, effectively telling the agent when this tool applies and when it does not. It does not point to a different tool for invoices that already have payments, so the routing guidance is implied rather than complete.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.