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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it discloses that this is a 'Premium API' with a specific cost of $0.25 USDC via x402, which is critical for an agent deciding whether to invoke a paid tool. It also lists the output dimensions, giving the agent expectations about the response.

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 with no filler. The first sentence front-loads the core purpose and output dimensions; the second adds the essential cost warning. Every word earns its place.

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-parameter read-only tool with full schema coverage and no output schema, the description is nearly complete. It covers what the tool does, what it returns, and the cost implication. The only minor gap is that it doesn't describe the response format or any error conditions, but with no output schema and a simple lookup parameter, this is acceptable.

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%, so the schema already documents the single 'lookup' parameter with an example. The description adds the context that the parameter is a phone number to profile, but it does not add format details beyond the schema's example. Baseline 3 is appropriate because the schema carries the parameter documentation burden.

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 ('Get profile') and resource ('phone number'), and enumerates the exact data dimensions returned: carrier, line type, geographic location, validation status, and risk assessment. This clearly distinguishes it from sibling tools like interzoid_ip_profile or interzoid_building_profile, which target different entities.

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 usage context by naming the resource type and the profile dimensions, but it does not explicitly state when to choose this tool over alternatives, nor does it mention any prerequisites or exclusions. An agent can infer that this is for phone numbers, but there is no explicit routing guidance relative to the many sibling tools.

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