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

Beyond the destructiveHint annotation, the description adds critical behavioral facts: the action cannot be undone and requires explicit user confirmation. It also explains the exact effect on the invoice record, which is more specific than the generic destructive hint.

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 two sentences with no filler. The first sentence front-loads the purpose and distinguishing effect, and the second sentence delivers the irreversibility and confirmation requirement.

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 mutation with three well-documented parameters, destructive annotation, and no output schema, the description covers the essential facts an agent needs: what voiding does, that it is irreversible, and that user confirmation is mandatory. No critical operational context 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?

Schema description coverage is 100%, so the schema already explains all three parameters. The description reinforces that confirmation is required but does not add meaning beyond the schema's 'Must be true' note, so the baseline score of 3 is appropriate.

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 names a specific verb and resource ('Void an invoice') and clarifies the operation's semantic scope: it keeps the record and number while zeroing amounts. This distinguishes void_invoice from delete_invoice and update_invoice without needing to inspect schemas.

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 makes the intended use case clear: voiding when you want to preserve the record and number rather than delete it. It does not explicitly name alternatives like delete_invoice, but the 'keeping the record and its number but zeroing its amounts' phrasing gives strong contextual guidance.

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