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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the description goes beyond that by explaining the parameter's effect on the result (Romania vs international, phone number type detection). It fully discloses the tool's conditional behavior, adding significant value over the 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?

Two well-structured sentences, the first stating purpose and the second detailing parameter behavior. No redundant words, and the most important info (purpose) is front-loaded. It is concise yet comprehensive.

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 single-optional-parameter tool with read-only and idempotent annotations and no output schema, the description covers all possible invocations (no arg, destination, phone number) and their outcomes. Nothing essential is missing for an agent to call it 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?

The schema describes the parameter only as 'name of country/destination or Romanian phone number' with 100% coverage. The description enriches this with concrete examples, notes that Romanian and English country names are accepted, and explains the phone-number case. This substantially clarifies what values are valid and what the tool will do with them.

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 tool returns ClickPhone rates for calls and SMS, and explains the behavior for both no-argument and argument cases. It distinguishes itself from sibling tools (cauta, pachete, etc.) by focusing specifically on rates, so an agent can easily select it for tariff inquiries.

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 gives explicit usage context: no argument returns Romania rates, a destination searches among 600+ destinations, and a phone number triggers fixed/mobile detection. It does not explicitly name alternative tools or state when not to use it, but the purpose is clear enough that an agent can infer when this tool is appropriate.

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