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

With no annotations, the description carries the full burden, and it does well by disclosing the key behavioral assumptions: IR is applied to the entire nominal gain, and the output exposes the net real rate after tax. It reveals the tax impact on inflation protection, which is a non-obvious behavioral trait. It doesn't discuss edge cases or exact output structure, but for a calculator this level is strong.

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 focused sentences: first states the function and components, second conveys the key output insight, third gives parameter guidance. Every sentence earns its place, no fluff, and the most important information 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?

For a calculator with no output schema, the description covers the inputs, the calculation logic, and the main output concept. It could be more explicit about the exact return format (e.g., whether it returns a breakdown or a single number), but the stated output ('quanto da proteção contra inflação o imposto leva') gives sufficient functional understanding. Given the 100% schema coverage and moderate complexity, this is nearly complete.

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 baseline is 3. The description adds value by explicitly grouping required (principal, real_rate, months) vs optional (inflation) parameters and instructing the agent to 'use exactly these names, in English'. This practical guidance helps prevent parameter-name translation errors and reinforces semantics already present in the schema.

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 uses the specific verb 'Simula' and identifies the exact resource: 'renda fixa IPCA+ (CDB ou Tesouro IPCA+)'. It enumerates the key computed outputs (taxa real contratada, inflação projetada, IR sobre o ganho nominal inteiro, taxa real líquida) and the unique insight (how much tax erodes inflation protection). This clearly distinguishes it from sibling tools like calculate_tesouro_prefixado or calculate_investment_return.

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 gives strong context by specifying the domain (IPCA+ fixed income, both CDB and Tesouro) and the calculation scenario. However, it does not explicitly name alternative tools or state when not to use it. The usage is implied rather than contrasted with siblings.

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