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

No annotations are supplied, so the description carries the full burden. It does disclose a meaningful trait — the returned token has a 24-hour lifetime — but it is silent on what happens when payment is not yet confirmed (error vs. pending status), whether repeated calls are safe/idempotent, and whether it mutates state to 'activate' access.

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?

One front-loaded sentence that states the verification step and the result with zero filler. Nothing is repeated from the schema or title, and the ordering (check payment → return token) mirrors the actual call flow.

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 covers the essential: what it consumes (an invoice from comprar_acesso) and what it yields (a 24-hour token). The remaining gap is failure/pending behavior, which matters because the tool is gated on a payment check.

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?

With a single parameter at 0% schema coverage, the description is the only source of meaning, and it does add key provenance: fatura_id is the invoice produced by comprar_acesso. It does not state the expected format or whether the id can come from elsewhere, but the provenance note is the essential context an agent needs.

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+resource pair ('Confere o pagamento de uma fatura') and names the concrete outcome ('devolve o token de acesso de 24 horas'), which lets an agent distinguish it from the sibling comprar_acesso. It stops just short of 5 because it doesn't explicitly contrast itself with the other siblings or state the scope of what it does not do.

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 only implied: by saying the fatura is 'gerada por comprar_acesso', it suggests this tool is the step after a purchase. There is no explicit 'use this when…', no statement about prerequisites (must a purchase exist?), and no alternatives or exclusions given.

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