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

No annotations are supplied, so the description carries the full behavioral burden. It usefully discloses that the call is free ('Sem custo'), but it says nothing about return format, units, whether the balance is per-key or shared, or what happens when quota is exhausted — all of which matter for a quota-checking tool.

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?

Two short sentences, front-loaded with the outcome and finished with the cost note. Every clause carries information and nothing is padded.

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 zero-parameter read tool this covers the essentials: what is returned and that it costs nothing. With no annotations and no output schema, though, the description could have said more about the shape or units of the balance returned, leaving a small but real gap.

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 tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description correctly implies the key is implicit from the session ('da chave usada'), which is the only 'input' concept here.

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 gives a specific verb ('Mostra') and a specific resource ('o saldo de créditos da chave usada e a cota grátis'), so the agent knows exactly what is returned. It does not name or contrast with any sibling, but the siblings (buscar_candidatos, detalhar_candidato, explorar, valores_dimensao) are unrelated, so confusion is unlikely.

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?

'Sem custo' hints that this is a free, safe call an agent can make at any time, which is useful usage context. However, there is no explicit statement of when to call it (for example, before other paid calls) and no reference to alternatives, so usage is only implied.

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