Pedir um numero

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

With no annotations, the description carries the full burden and does so: it discloses that the balance is debited immediately (a real cost side effect), the ~20-minute lifetime of the number, and that cancellation refunds the value. It also tells the agent what the call returns (activation id and phone).

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?

Four tightly packed sentences: action and cost first, then the return value and next step, then the time limit and refund path. No sentence is redundant and the most decision-relevant facts (cost, expiry, refund) are front-loaded.

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?

There is no output schema and no annotations, so the description must cover the return and safety profile itself — and it does, naming the returned activation id and phone plus the expiry/refund behavior. Nothing an agent needs to invoke this correctly is missing.

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 100%, so the schema already documents all four parameters (ddd, apiId, country, serviceId) and their defaults. The description adds no parameter-level detail beyond the schema, which is the baseline 3 case.

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 and resource ('Compra um numero virtual') plus the exact purpose (receber o SMS de verificacao). It also names what is returned and routes the agent to siblings, so it is distinguishable from the other activation tools at a glance.

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?

Gives explicit follow-up routing: use wait_for_sms or get_activation to read the code, and cancel_activation if the SMS never arrives. The ~20-minute validity window tells the agent when the number expires, which is exactly the condition that selects the cancel path.

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