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

Annotations already establish that the operation is read-only, idempotent, and non-destructive. The description adds useful operational context beyond that profile, particularly code extraction and the paid add-on prerequisite, though it leaves history limits, ordering, and empty-result behavior unspecified.

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?

Two short sentences front-load the purpose and resource scope, then state the billing prerequisite. There is no redundant or unnecessary wording.

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 simple one-parameter read tool, the description supplies enough scope and prerequisite information to support correct invocation alongside the schema and annotations. The absence of an output schema makes the lack of result-shape or retrieval-history details more noticeable, and sibling routing remains incomplete.

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 id parameter is already documented as a phone resource UUID. The active/owned wording adds a modest eligibility constraint, but the description does not explain where to obtain the UUID or add further invocation details.

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 action and resource: reading received SMS messages and extracted codes for an active owned phone number. It does not explicitly distinguish this existing-message read from the sibling wait_for_sms or list_phone_numbers tools.

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 active owned-number scope and active paid add-on requirement provide concrete usage context and prerequisites. However, there is no guidance on when to choose wait_for_sms instead, or how list_phone_numbers can help supply the required resource ID.

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