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

No annotations are provided, so the description carries the disclosure burden. It does disclose the meaningful behavior: it applies the regressive IOF table, deducts 22.5% IR on the remainder, and even compares against waiting until day 30. That is substantial behavioral information for a calculator with no side effects.

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?

One dense, front-loaded sentence states the purpose and calculation scope, followed by a compact parameter note. Every clause earns its place and the critical 'before 30 days' condition appears at the beginning.

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 deterministic calculation with no output schema, the description gives the legal basis, the assets covered, and the parameters. It is complete enough for an agent to select the tool, though it does not specify the shape of the return value.

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 input schema already documents all three parameters at 100% coverage (principal, days, cdi_percent). The description restates which are required/optional and insists on exact English parameter names, which is useful but adds no semantic depth beyond the schema, so the baseline of 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 opens with a specific action and resource: 'Calcula quanto o IOF come de um resgate feito antes de 30 dias' and lists the exact pieces of the calculation (Decreto 6.306 regressive table, 22.5% IR, waiting comparison). It is clearly not a tautology, but it never names or contrasts a sibling tool, so it stops one step short of full differentiation.

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 gives a clear trigger context: redemptions before 30 days for caixinha, CDB, and Tesouro. That tells an agent when to reach for it. It does not explicitly list exclusions or name alternatives, so it earns context but not the upper bound.

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