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

No annotations are provided, so the description carries the full behavioral burden. It discloses the key calculation assumptions: compounding of the contracted rate, regressive IR, B3 custody fee of 0.20% per year, and exclusion of the Selic-only exemption. It does not specify the exact return shape, rounding, or edge cases, but the main behavioral traits are explicit.

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 dense but well-organized: it front-loads the scope and modeled factors, then gives the required parameters and a naming instruction. Every sentence earns its place, and the Selic exclusion is useful differentiation rather than padding.

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 3-parameter simulation with no output schema, the description is mostly complete: it defines all required inputs by name and states what is modeled. The main gap is that it does not describe the shape of the result beyond 'taxa líquida anual efetiva', so an agent cannot know whether gross final value, IR amount, or custody fee are also returned.

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 description coverage is 100%, so each parameter already has a semantic description. The description only restates the required parameter names and instructs the agent to use exactly those English names, which adds no meaning beyond what the schema provides.

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 'Simula o Tesouro Prefixado até o vencimento', a specific verb+resource statement that clearly identifies the tool's purpose. It then enumerates the modeled components (compounded contracted rate, regressive IR, 0.20% p.a. B3 custody, net effective annual rate) and explicitly distinguishes it from Selic by noting 'sem faixa isenta, que é só do Selic'.

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 provides clear context and an implicit when-not by stating that the exempt band belongs only to the Selic title, which helps an agent avoid using this tool for the wrong Tesouro type. It does not explicitly name the alternative tool such as calculate_tesouro_selic, but the context is sufficient for basic routing.

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