Verify any phone number with country code to confirm validity and obtain carrier and country information. Resolve invalid numbers before sending messages.
Verify if a phone number is valid and get carrier/country info. Costs 2 credits.
| Name | Required | Description | Default |
|---|---|---|---|
| phone | Yes | Phone number to verify (with country code, e.g. +1234567890) |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries behavior disclosure itself. It discloses the credit cost ('Costs 2 credits'), which is a non-obvious side effect, and presents the operation as read-only verification. It does not specifiy response structure or failure modes, but for a simple verify tool the behavior is adequately transparent.
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 short sentences: one states the core function and outcome, the second states the cost. No fluff or repeated information; the most important operational detail (cost) is included without bloating the description.
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 verification tool, the description covers purpose, input format through the schema, and cost. It does not detail return value formatting, but it communicates the essential result categories (validity, carrier, country) adequately for selection and invocation.
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%, and the phone parameter already includes a format example with country code (e.g. +1234567890). The tool description adds no per-paramter information beyond what the schema provides, so baseline 3 is appropriate.
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?
States a specific action ('Verify') on a specific resource ('a phone number') and the primary outcomes: validity plus carrier/country info. This clearly distinguishes it from sibling tools like haul_verify_email and haul_check_balance.
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 resource and outcome make the intended use clear: verifying phone numbers. It does not explicitly name alternatives such as haul_verify_email for email verification, but the sibling context and targent resource provide sufficient context with no misleading exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.