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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It explains the core calculation behavior for both direct and inverse cases, but does not disclose return values, rounding behavior, or edge cases such as division by zero. This is adequate for a simple calculator but not richly transparent.

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: the main purpose appears first, followed by concise direct/inverse explanations and parameter guidance. Every sentence contributes useful information with no filler or repetition.

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 simple four-parameter calculator with a fully documented schema, the description is nearly complete. It covers required and optional parameters, the distinction between direct and inverse, and even warns about parameter naming. The only notable gap is the lack of explicit return-value information, since there is no output schema.

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 parameters with 100% coverage. The description adds value by explicitly naming a, b, and c as required, inverse as optional, and by explaining the proportional relationships between them. This goes beyond the schema's standalone value labels.

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 starts with a specific verb and resource: 'Resolve regra de três simples, direta ou inversa.' It clearly explains both direct and inverse proportionality, which distinguishes it from the many other calculate_* siblings and leaves no doubt about what the tool computes.

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 clear usage context by explaining when direct applies ('se A está para B, C está para quanto') and when inverse applies ('quando um valor sobe e o outro desce na mesma proporção'). It does not explicitly name alternative tools or exclusion conditions, but the context is sufficient for an agent to recognize the appropriate scenario.

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