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

With no annotations, the description carries the burden and it does disclose notable behavior: results use 'IR regressivo descontado', compare with 'a poupança', and use today's 'Banco Central' CDI. It also clarifies that cdi_percent can represent partial or full CDI, but it does not describe exact return values.

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 terse sentences: outcome first, options second, parameter usage third. Each sentence adds distinct guidance, and there is no filler or unnecessary restatement.

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 three-parameter calculator, the description names required and optional parameters, gives an example, and flags behavioral details such as IR and savings comparison. The absence of an output schema makes the lack of explicit return-format detail a minor gap, but it would not prevent 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%, so the description adds only modest value beyond the schema: an example like '102% de um CDB', a note that cdi_percent is optional, and an instruction to use exact English parameter names. Most parameter meaning already lives in the input 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 opens with a specific verb and resource: 'Calcula quanto rende um valor no CDI de hoje (Banco Central) por um prazo em meses'. It further distinguishes the tool by mentioning regressive IR and savings comparison, making it clearly distinct from generic savings/investment siblings.

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 states the calculation context and required parameters, but it does not explicitly say when to choose this tool over siblings like calculate_savings_return or compare_with_cdb. The intended use can be inferred from the CDI-specific wording, so guidance is implied rather than explicit.

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