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

The annotation destructiveHint=true already signals destructive behavior. The description adds the critical detail 'Ação irreversível' (irreversible action) and the justification requirement, going beyond the generic annotation without contradicting it.

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 unnecessary words. It front-loads the action and includes all essential information (requirements and irreversibility) efficiently.

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 simple cancellation tool with a complete schema and destructive annotation, the description adequately covers purpose, prerequisites, and consequences. It could mention the success outcome, but this is not critical given the tool's straightforward nature.

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 already describes all parameters with 100% coverage, including examples and minLength. The description reiterates the reference and justification but does not add new semantic meaning beyond what the schema provides, so 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 clearly states the action ('Cancela uma NFS-e') with a specific resource and scope ('emitida anteriormente'). This distinguishes it from sibling tools like emitir_nfse and cancelar_webhook by focusing on NFS-e cancellation.

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 provides clear prerequisites (reference and mandatory justification) and implies usage context (previously issued NFS-e). However, it does not explicitly state when not to use the tool or mention alternatives, though the context is sufficient for an agent.

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