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

The annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds a behavioral nuance about network-dependent results and placeholder patterns, but these are vague and do not fully disclose side effects or error conditions. Since the description does not contradict the annotations, a middling score reflects the partial extra information.

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 brief (three sentences) without fluff, but the structure is disjointed: it jumps from purpose to parameter hint to behavior note without logical flow. It is concise but not well organized enough to clearly convey the tool's functionality.

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?

Given the schema has 6 parameters, 2 required, and enums, the description fails to explain the role of each parameter or the meaning of the required fields. Even though an output schema exists, the parameter semantics and usage context are under-specified, making this description insufficient for reliable tool selection.

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?

With zero schema description coverage, the description must compensate. It mentions 'origin' and 'destination' and 'phone number' but does not map them to the six parameters or explain the enums (detail, device) or the format constraints. The agent would still be guessing about what each parameter expects.

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 states a verb ('prepare') and object ('dialing guidance') but does not concretely define what that guidance entails or what the output looks like. 'Origin-specific' and 'reviewed countries' are ambiguous, and the description does not differentiate it from sibling tools like 'format_international_phone_number' or 'lookup_country_calling_code'.

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 a partial hint about parameter usage ('no phone number returns safe placeholder patterns') but does not clarify when this tool is preferred over alternatives. It lacks any explicit mention of conditions or exclusions, leaving the agent to infer when to choose this tool.

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