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

The readOnlyHint annotation already indicates a safe read operation, so the description only needs to add extra behavioral context. It adds the legal basis and NCM-based scope, but does not disclose the return format or behavior when optional parameters like dataDoFato or quantidade are omitted.

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 a single, front-loaded sentence that directly states the tool's purpose. No unnecessary words or filler.

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?

Given the moderate complexity of a tax calculation tool with four parameters and no output schema, the description is somewhat minimal. It does not explicitly state the return value or the significance of optional parameters, but the read-only annotation and clear purpose make it adequate for basic understanding.

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 schema already documents all parameters. The description adds minimal value beyond 'com base no NCM', which is largely redundant with the schema's ncm description. It does not explain the purpose of optional parameters like quantidade or dataDoFato.

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's function: 'Calcula o Imposto Seletivo (IS) sobre um produto com base no NCM'. It uses a specific verb ('Calcula') and resource ('Imposto Seletivo'), and includes legal references (EC 132/2023 + LC 214/2025) that distinguish it from sibling tax tools like calcular_cbs_ibs and simular_imposto_reforma.

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 provides no guidance on when to use this tool versus alternatives. It does not mention that this is for IS specifically while other tools handle CBS/IBS or regime simulation, nor does it state any prerequisites or exclusions.

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