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

With no annotations, the description carries the full burden, and it does disclose a meaningful trait: 'Public — no authentication required.' The verbs 'Inspect' and 'view' also implicitly signal a read-only operation. It does not cover response format, rate limits, or error behavior, so there is room to improve, but it goes beyond a bare restatement of the tool's name.

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, with the core purpose front-loaded in the first sentence and the auth context in the second. Every phrase earns its place, and the colon-separated list keeps the capabilities scannable.

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 one-parameter read-only lookup with no output schema, the description supplies the essential context: purpose, scope (Moroccan operators or international), the applicable rate, and the fact that it is public. It would be more complete with a note about what the result looks like, but the missing detail is minor given the tool's simplicity.

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?

The input schema already documents the single parameter 'to' fully (national or E.164 format), giving 100% schema description coverage. The description adds no new parameter-level guidance beyond what the schema states, so the baseline of 3 is appropriate.

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 opens with a specific verb, 'Inspect', and a concrete resource, 'a phone number', then enumerates three distinct capabilities: validating format, identifying Moroccan operator or international country, and viewing applicable rate. This clearly differentiates it from sibling tools like get_pricing (price list) or send_sms (sending), which operate on different objects.

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 implies when the tool is relevant—when someone needs to validate a number or check its operator/rate—but it never explicitly contrasts it with alternatives such as get_pricing or mentions when not to use it. The 'Public — no authentication required' note gives some context, but it is about auth, not selection among siblings.

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