order_number

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

With no annotations provided, the description must disclose behavioral traits, and it does so effectively: the number is private, exclusive to one activation, held for 20 minutes, and money is held now but charged only when the code arrives. These details go beyond the schema and give the agent important non-obvious information about the tool's behavior.

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 description is two sentences long, with the main purpose front-loaded in the first sentence and the key behavioral details in the second. Every word earns its place, and there is no redundant or filler content.

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 tool with no output schema and no annotations, the description covers the essential context: the ordering process, the exclusivity, the 20-minute hold, and the payment model. It does not mention what the response returns (e.g., an activation ID), but that is not required given the absence of an output schema. Minor missing details like prerequisites (funds) are implied by 'Money is held now'.

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?

All four parameters have descriptions in the schema (100% coverage), so the baseline is 3. The description does not add any parameter-specific details beyond what the schema already provides, but the schema is sufficiently descriptive (e.g., 'Country id from list_countries', 'Ceiling per activation'). Thus the description adds no extra value 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 clearly states the tool's action: 'Order a private number for one service in one country.' This specifies the verb ('order'), the resource ('private number'), and the scope ('for one service in one country'), distinguishing it from siblings like list_services or wait_for_code. The purpose is unambiguous and complete.

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 description provides clear context that this is the initial step to obtain a number for a single service and country, including the 20-minute hold and payment timing. It does not explicitly state exclusions or alternatives, but the purpose is distinct enough from the sibling tools that an agent can infer when to use it. The absence of explicit 'when not to use' guidance prevents a 5.

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