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

Annotations already declare destructiveHint=true, but the description adds substantial value by explaining exactly what destruction entails: invoice can no longer be paid or edited, existing payments are preserved as history. Also discloses the state restrictions, enriching the annotation without contradiction.

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 sentences, front-loaded with the core purpose. Every clause adds essential information including constraints and side effects. No wasted words.

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?

Given the low complexity (single parameter) and the presence of an output schema, the description fully covers what the tool does, what happens, and what cannot be done. It provides complete operational context for an AI agent.

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 covers the single parameter invoiceId with a clear description. The tool description adds no further parameter details, but since schema coverage is 100%, the description need not compensate. Baseline 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 states 'Void an invoice' with a specific verb and resource, and clarifies the meaning of voiding (cannot be paid or edited). It distinguishes the tool from siblings like delete_invoice and restore_invoice by explaining the unique state transitions.

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?

Provides clear context for when to use the tool (to void an invoice) and includes a key exclusion: cannot void invoices that are already PAID or VOIDED. Does not explicitly mention alternatives, but the constraints and purpose make usage clear.

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