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

There are no annotations, so the description carries the behavioral burden. It does disclose the conditional formula (0.5% + TR when Selic > 8.5%, else 70% of Selic + TR), which is meaningful. However, it does not clarify how TR is sourced or applied, nor what happens at the exact 8.5% boundary.

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?

Two dense sentences convey purpose, legal rule, and parameter guidance without fluff. The first sentence is long but packs the essential calculation rule; the second sentence is slightly redundant with the schema's required array but earns its place by emphasizing exact parameter names.

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?

Inputs and the core rule are well covered, but there is no output schema and the description does not state what the simulation returns (final balance, monthly breakdown, total yield). It also omits edge-case behavior for selic_annual exactly 8.5%, which matters for a conditional rule.

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 baseline is 3; the description adds value by explicitly listing required versus optional parameters and insisting on the exact English names. This is especially useful because the parameter descriptions are in Portuguese and the agent might otherwise localize the names.

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 states a specific action ('Simula o rendimento da poupança') with a clear resource and scope: savings account yield with monthly contributions. It also anchors to a specific legal rule (Lei 12.703/2012), distinguishing it from generic investment calculators among siblings like 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 clearly sets the context for use: savings yield simulation with monthly deposits and Selic-based legal remuneration. It does not explicitly name alternatives or say when not to use it, but the scenario is specific enough that an agent can route to it correctly among many calculate_* siblings.

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