Get phone info

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

Annotations already declare readOnlyHint=true, so safety is covered. The description adds a meaningful behavioral detail: it returns the number normalized to international format, and explains why (e.g., 'when the user wrote it with spaces or brackets'). This goes beyond the schema and annotates the tool's transformation behavior without contradicting the read-only hint.

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 sentences, no filler. The core purpose and returned fields are front-loaded, and the normalization detail is added as a clarifying note. Every sentence earns its place; the structure is efficient and 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?

This is a simple single-parameter, read-only lookup tool, and the description fully covers what it does, why it is useful, and what it returns (country, operator, brand, normalized number). No output schema exists, but the description names the return fields explicitly, making it complete for an agent to call 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 description coverage is 100% (pattern and example provided), so the schema already documents the parameter format. The description adds semantic value by explaining that the tool normalizes input like spaces/brackets to international format, which clarifies expected input and output behavior beyond the schema's pattern.

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 specific verb ('Look up') and resource ('phone number information') and explicitly lists the data returned (country, mobile operator name and brand). It also mentions a concrete use case ('before sending to verify the number'), which distinguishes it from sibling tools like send_message or get_delivery_status.

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 provides clear context for when to use the tool ('Useful before sending to verify the number and determine routing'), which implies appropriate timing and purpose. It does not explicitly name alternatives or exclusions, but the context is enough for an agent to infer that it is not for sending or post-send status checks.

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