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

Annotations already declare readOnlyHint, destructiveHint, idempotentHint, which the description aligns with. Additionally, it discloses the aggregation behavior (accounts[] + errors[]) and the limitation about available limit, adding value beyond annotations.

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 well-structured with line breaks and front-loads purpose. It is slightly verbose but every sentence adds value. Could be more concise by omitting explanatory notes about Conta Simples API limitations, but those add useful context.

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?

The description covers both modes and explains return fields (total, amountToPay, dates, paymentStatus, items). It also addresses the missing limit field explicitly. Without output schema, it gives enough information to understand the tool's output. Slightly incomplete regarding pagination or error handling.

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 description coverage is 0%, so the description fully explains parameters: due_date changes mode, status is optional filter, accounts enables parallel aggregation. Though status enum values are not listed, the description provides sufficient context for usage.

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's about credit card invoices (faturas do cartão de crédito) and distinguishes two modes: listing invoices and retrieving details with due_date. It differentiates from sibling tools like contasimples_balance and contasimples_card.

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 when to use each mode (without due_date for listing, with due_date for details) and mentions that it doesn't expose available limit, implying not to use for limits. However, it doesn't explicitly compare to other tools or provide exclusionary guidance.

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