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

No annotations are provided, so the description carries this burden. It discloses the calculation/comparison behavior and the output concept ('Mostra o custo real de pagar o mínimo'), and 'Calcula' implies a read-only operation. It does not describe input assumptions or edge cases, but nothing contradicts the schema.

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?

Three short sentences cover function, output, and parameter requirements with no filler. Every sentence 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 calculator with no output schema and no annotations, the description gives essential call context: purpose, required/optional parameters, and the English-naming caution. It lacks an explicit output structure and edge-case guidance, so it is not a 5, but it is sufficient for correct invocation.

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%, with type, range, and default descriptions for all five parameters. The description adds a line telling the agent exactly which names are required vs optional and to use English parameter names, which is genuinely useful for this Portuguese-labeled tool.

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 ('Calcula'), a precise resource ('juros do crédito rotativo do cartão'), and a comparison target ('parcelamento da fatura'). This clearly distinguishes it from generic sibling calculators such as calculate_installment and compare_loans.

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 first sentence establishes a clear scenario: comparing revolving credit interest against invoice installment. It does not explicitly name alternatives or exclusions, but the context is clear enough for an agent to select it appropriately.

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