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

Annotations already declare this a safe read (readOnlyHint true, destructiveHint false), so the bar is lower. The description does add real value by disclosing the polling contract and its two termination conditions, but it says nothing about overall timeout, cost per poll, or number expiry, which matter for a paid activation flow.

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?

Three short sentences, front-loaded with the resource and immediately followed by the action and the polling rule. The opening fragment 'One-time SMS numbers.' is nearly redundant with the sentence that follows it.

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?

An output schema exists, so return field semantics need no explanation here; the description correctly focuses on the polling behavior an agent would otherwise get wrong. Only the failure/timeout path and any cost implications are left uncovered.

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 coverage is 100% and the single parameter already documents that it is the activation UUID from sms_activation_buy_number. The description adds no syntax, format, or sourcing detail beyond that, so 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?

States a specific verb and resource: 'Poll for the SMS code of a one-time number.' The 'one-time' qualifier implicitly separates it from the rental siblings, though it never names sms_rental_get_codes explicitly.

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 concrete usage guidance: call repeatedly every few seconds until `done` is true or `codes` is non-empty. That is clear operational context, but it offers no exclusion against sms_rental_get_codes or advice on what to do if no code ever arrives.

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