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

Beyond the readOnlyHint/destructiveHint annotations, the description discloses that nothing is persisted, the exact computed outputs (monthly amount, total paid, total interest, projected balance impact including negative months), and the simulation nature. It reinforces and expands on the annotations without contradicting them.

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 dense sentences carry purpose, input rules, output summary, and the alternative tool. The most important scoping information (simulation, one debt, exclusive parameters) is front-loaded, and every phrase earns its place.

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 read-only simulation with an output schema, the description covers what the tool does, what inputs are allowed, what it returns, and what to use instead for real changes. An agent has everything it needs to invoke it correctly and avoid confusing it with update_debt.

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 coverage is 100%, so the schema already documents all three parameters. The description adds real value by explaining the mutually exclusive relationship between targetMonths and monthlyPayment, and by linking each one to its computed result, which the schema alone does not convey.

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 opens with a specific verb and resource: 'Simula a quitação de UMA dívida' (simulates paying off one debt), and immediately clarifies it is a simulation, not an actual write. It distinguishes itself from update_debt by name, so an agent can tell planning from execution.

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 explicitly states the two possible input modes (targetMonths OR monthlyPayment), forbids using both ('nunca os dois'), and tells the agent to use update_debt(remainingAmount) instead when the goal is to actually reduce the balance. This gives clear when/when-not guidance.

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