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

With no annotations, the description carries the full burden and does disclose two important traits: the tool mutates state (credits the balance) and does so idempotently ('uma vez só'), which tells an agent repeated calls are safe. It omits what happens when payment is absent or pending, whether authentication beyond session_id is needed, and any error behavior, so the disclosure is partial rather than complete.

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?

A single front-loaded sentence with the action first, followed by the idempotency caveat and the return values. No filler, no redundancy.

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?

Although there is no output schema, the description names the three return fields (paid, credited, balance), which covers the return contract. What remains missing is the failure/pending path and any auth or rate expectations, which matter for a state-mutating, likely-polled tool.

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 has one required parameter (`session_id`) with 0% description coverage, and the description never explains what the session id is, where it comes from, or how it relates to the buy_credits flow. With coverage this low, the description should compensate but does not.

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?

States a specific verb pair (check payment, credit balance) on a specific resource, and ties itself to the sibling buy_credits link, so an agent knows this is the post-purchase verification step. It stops short of contrasting with other credit/account siblings like `account`, but the purpose is unmistakable.

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 phrase 'pagou o link de buy_credits' implies the tool should be called after invoking buy_credits to confirm payment, which is useful implied usage. However, there is no explicit when-to-use/when-not guidance, no mention of polling cadence, and no pointer to an alternative if the payment hasn't landed.

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