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

With no annotations, the description carries the full disclosure burden. It discloses that it uses the current Central Bank CDI, returns post-IR net yield, and shows R$ differences per option. It does not mention data freshness, network dependence, or any assumptions about the fixed alternatives.

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 compact and front-loaded with the core comparison purpose, followed by the output behavior and parameter contract. Every sentence earns its place, though the parameter list somewhat duplicates the schema's required-field information.

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?

The description covers inputs, outputs, and the CDI source, but because there is no output schema and no annotations, it leaves some gaps: the exact return shape is not specified, and the modeling assumptions for Tesouro Selic, LCI/LCA, and savings alternatives are only implied.

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 four parameters at 100% coverage, so the baseline is 3. The description adds value by explicitly grouping required vs optional parameters and instructing the agent to use the exact English parameter names, which reduces localization mistakes despite the Portuguese description.

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 clearly states the tool compares a CDB earning X% of CDI against Tesouro Selic, LCI/LCA, and savings, and returns net post-IR yield and R$ differences. It is specific about the resource and outcome, though it does not explicitly name or contrast a sibling tool like compare_investments or calculate_lci_lca.

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 implies when to use the tool: when comparing a CDB against alternative Brazilian investments using current CDI. However, it gives no explicit guidance about when not to use it or which sibling tool to prefer for related comparisons, such as compare_investments or calculate_cdi_yield.

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