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

With no annotations, the description carries the behavioral disclosure burden. It clearly states that this is a one-time paid operation, the package amounts, and that the returned token is consumed by other APIs. It does not detail reversibility or failure scenarios, but the core side effect is 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 entire description is one efficient sentence with no filler. It front-loads the main action ('Recarrega crédito') and packs the payment method, package options, and return behavior into a compact structure.

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 one-parameter tool with no output schema, the description explains the input values, the payment mechanism, and the return value (the token). It is slightly light on operational context such as how the x402 payment is executed or what errors may occur, but an agent can likely call it correctly.

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 already documents the parameter well at 100% coverage, listing the valid values '1, 5, 10 ou 25'. The description adds the 'dólares' and 'pacotes' framing, which is helpful but largely redundant with the schema description.

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 uses a specific verb ('Recarrega crédito') and identifies the exact resource and mechanism: paying via x402 in fixed dollar packages and receiving a token. This clearly distinguishes it from related siblings like credito_saldo, since it explains the recharge/token-return flow.

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 intended use is implied: an agent should call this to add credit before using other APIs. However, it does not explicitly state when to use this tool versus alternatives such as credito_saldo, nor does it mention when not to use it.

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