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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, covering the safety and determinism profile. Absent an output schema, the field enumeration adds useful signal about what comes back, but the description never says whether the call is synchronous or returns a pending job id (relevant given the sibling check_async_status).

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 purpose sentence is front-loaded and efficient, but the raw 30-field dump in parentheses is unstructured padding that reads like a schema listing rather than guidance. It is not egregiously long, but the parenthetical does not earn its full space in its current form.

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?

With one required parameter, no output schema, and annotations covering safety, the field list partially substitutes for the missing output schema. What remains missing is the async/sync calling pattern and the relationship to the check_mobile_start / check_async_status siblings, which are central to using this tool correctly.

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 0%, so the description must compensate, and it does supply the required input format (international prefix, example +39) for the single 'mobile' parameter. It stops short of giving the full expected pattern such as an E.164 example, but the essential format constraint is conveyed.

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+resource ('Retrieves advanced information about a mobile number') and enumerates the returned fields, making the subject matter unambiguous. It does not, however, differentiate itself from sibling check_mobile_start or explain the 'advanced' vs 'start' distinction, leaving sibling selection to inference.

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 only guidance is an input-format note ('with international prefix es +39'), which is about how to call it, not when. Nothing tells the agent when to choose this over check_mobile_start or whether a result must be fetched via check_async_status.

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