Swap Phone Number

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

Annotations already indicate a non-read-only, non-destructive mutation, and the description adds meaningful behavioral context: the 120-second cooldown, the cooldown_active error returned locally, the no-additional-charge guarantee, and the no-backend-round-trip detail. No contradiction with annotations.

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 well-structured sentences, front-loaded with the core action and outcome, followed by a bolded cooldown warning and error behavior. Every sentence earns its place with no fluff.

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 low-complexity, one-parameter mutation tool, the description covers use case, preconditions, cost implication, cooldown, and error behavior. The only minor gap is that it doesn't explicitly state what happens to the old number or what a successful response contains, but the operation's effect is reasonably implied.

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% and the single order_id parameter is already described with its status requirement. The description adds no parameter-specific meaning beyond the schema, so the baseline 3 applies.

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 and resource ('Swap a phone number on an existing order') and explains the concrete outcome ('Gets a new number for the same service and country without additional charge'). This clearly distinguishes it from sibling tools like create_order, retry_order, and cancel_order.

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?

It explicitly states when to use the tool ('Use when the current number isn't receiving SMS') and gives a concrete precondition ('Check swap_available_at on the order before calling'). It does not name alternative tools or when-not-to-use scenarios, so it stops short of a 5.

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