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

With no annotations, the description carries the behavioral burden and does well: it explains that both balance forms share the same balance, that notas_restantes counts XML with certificate, that Enterprise XML without certificate costs double, and that the call uses the FiscalAPI key without consuming a consultation. It does not explicitly describe read-only safety, but the balance-checking nature and the consumption rules are otherwise well disclosed.

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, first stating what balance is returned and then adding the key consumption rules. Every sentence contributes useful meaning, with no redundant restatement of the title or schema.

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 zero-parameter balance-checking tool with an output schema, the description is complete enough: it explains the two balance categories, their shared pool, and the special XML consumption rule. Return values are covered by the output schema, so the description does not need to enumerate them.

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 tool has zero parameters, so the baseline is 4 and there are no parameter semantics for the description to compensate for. The schema already fully covers the empty argument object.

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 resource and outcome: it reports the remaining account balance split into consultas_restantes and notas_restantes. It clearly differs from sibling tools that perform consultations, but it does not explicitly name those siblings or say how it relates to them, so it is clear rather than fully differentiated.

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 implies the tool is a non-consuming balance check using the FiscalAPI key, which helps an agent understand its role. However, it does not explicitly say when to call it versus proceeding directly with a consultation, nor does it give when-not-to-use guidance.

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