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

The annotations already flag destructiveHint=true and readOnlyHint=false, and the description adds meaningful behavioral detail: it overwrites currentInvoice on all cards unconditionally, returns previous and new values per card, and defines the needsCorrection threshold. This goes well beyond what the structured annotations provide.

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 three dense sentences with no filler: the first states the main side effect and scope, the second describes the return payload, and the third gives the operational trigger. Every sentence earns its place and the most important behavior is front-loaded.

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 no parameters, a destructive annotation, and an output schema, the description supplies the remaining essential context: when to run it, what it mutates, and what it returns. There is no critical missing information for an agent to call 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?

The tool has zero parameters, so parameter documentation is not needed; the baseline for no-parameter tools is 4. The description correctly focuses on behavior rather than inputs, leaving nothing ambiguous about how to invoke it.

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 a specific action ('Recalcula e sobrescreve currentInvoice') and a precise scope ('de TODOS os cartões do usuário, incondicionalmente'), which clearly distinguishes it from invoice-reading siblings like current_invoice or get_invoice. The clarification that it acts on all cards, not just misaligned ones, removes ambiguity about its intent.

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 explicitly says when to run: after batch operations such as transaction reimport that may have desynchronized Card.currentInvoice. It does not name specific alternatives or state when not to use the tool, but the trigger condition is concrete enough for an agent to select it correctly.

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