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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is well covered. The description adds behavioral context about the date filtering and the default of returning all data when no dates are provided, which goes beyond the schema. No contradictions.

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 sentence, front-loaded with the core purpose, and the date logic is succinctly expressed. Every word earns its place, no fluff.

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 simplicity (2 optional params, no output schema, no nested objects) and rich annotations, the description is largely complete. It explains the grouping dimensions and the date behavior. It could mention that the output is aggregated by month, but that's implicit in the grouping; with no output schema, it's a minor gap, but the description is adequate for a read-only balance query.

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 schema describes the two parameters only as strings with no format or meaning. The description explains that they are optional dates in YYYY-MM-DD format that limit the window and that omitting them returns all data. This adds value, but since the schema coverage is 0%, the description partially compensates. However, it doesn't clarify the expected format for the date range (e.g., inclusive rollover) or any other specifics, so it stays at a baseline.

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 it retrieves the user's balance, grouped by multiple dimensions (bank, category, payment method, card, type, month), differentiating it from sibling tools like poupa_retrieve_transactions (transactions list) and poupa_banks (bank list). It uses a specific verb ('Saldo do usuário') and resource, making the purpose unambiguous.

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 explains the optional date range and its behavior ('start_date/end_date limitam a janela; sem datas, traz tudo'), which is clear usage context. It doesn't explicitly mention when to prefer this over alternatives, but the grouping purpose implicitly distinguishes it from transaction retrieval tools, and the sibling list provides enough contrast.

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