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

No annotations are provided, so the description carries the full behavioral burden. It usefully discloses the cost and payment method ($0.005 USDC on Base via x402) and the supported identifier scope, but it omits return semantics, error behavior, and whether value formatting must be normalized before calling.

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 two short sentences, front-loads the purpose and supported types, and adds the pricing detail without waste. Every element earns its place for this simple validation tool.

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?

With no annotations and no output schema, the description should carry more of the behavioral contract. It covers supported types and payment, but it leaves the return value (e.g., boolean, status, error details) and input format requirements for each identifier type unstated.

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 must compensate for both parameters. It does expand the enum by naming CPF, CNPJ, EAN-13, NF-e, and phone, and adds that CNPJ may be numeric or alphanumeric, but it says nothing about the required 'value' format for each identifier type.

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 verb (validate) and resource (Brazilian identifier), then enumerates the supported identifier types. This makes the tool readily distinguishable from siblings such as decode_boleto, decode_pix, and lookup_bank.

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?

Usage is implied by the identifier types listed and the verb 'validate'; an agent can infer it should use this tool when checking CPF, CNPJ, EAN-13, NF-e, or phone values. However, it gives no explicit when-to-use guidance, no prerequisites, and does not name alternatives for related decode/lookup tasks.

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