check_phone

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

Annotations already indicate read-only, idempotent behavior. The description adds context that validation is performed offline using libphonenumber and that VoIP/invalid numbers are flagged as red flags. No contradiction with 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?

Extremely concise: two sentences covering purpose and usage. No filler, front-loaded with the core function. Every sentence is valuable.

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 tool's moderate complexity and the presence of an output schema (not shown but confirmed), the description covers the main behavioral aspects including offline validation and red flag indicators. It lacks details about required permissions or prerequisites, but these are implied by the read-only annotation.

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 description does not add meaning beyond the input schema, which already has descriptions for each parameter. With schema description coverage at 0%, the description should compensate but fails to explain parameter usage or formats in detail.

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's purpose: validating a phone number, including checking validity, type (mobile/VoIP/premium), region, and carrier. It uses specific verbs and resources, and is distinct from sibling tools that check other types of data like emails or domains.

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?

Provides a concrete use case ('a recruiter gives a phone/WhatsApp number'), giving context for when to use the tool. However, it lacks explicit guidance on when not to use it or mention of alternative tools for related tasks.

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