WhoisFreaks

Subdomain typosquatting search

subdomainTyposquatting

Read-onlyIdempotent

Find subdomains, on any domain, that contain a typo variant of a brand name or match a wildcard pattern as one of their labels, for example login.paypa1.example.com. Phishing pages often hide a brand inside a subdomain of an unrelated domain, so these hosts never show up in domainDiscovery. Use this for brand protection and phishing hunting. Provide exactly one of keyword or pattern. For the subdomains of one domain use subdomainLookup. To judge how risky a result's domain is use domainReputation. Costs 5 credits per page (100 subdomains by default). Returns each subdomain with its registrable domain, whether it is active, and its first-seen, last-seen and inactive-from dates, plus the total count. When there are more, the result has a nextPageToken: pass it as pageToken, with the same keyword or pattern, to get the next page. Behavior: read-only. Makes one request to the WhoisFreaks API using your WhoisFreaks API key (the WHOISFREAKS_API_KEY environment variable, or on the hosted server the key sent with the request) and uses that account's API credits; nothing is created or changed. If the call fails, the result is a short message instead of data, for example: key invalid, or plan or credits used up (HTTP 401), domain extension not supported (HTTP 403), no data found (HTTP 404), or rate limit reached (HTTP 429).

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "subdomainTyposquatting"
  }
}

Input Schema

Name	Required	Description
`keyword`	No	Brand or name to find typo variants of inside subdomains: 3 to 63 letters, digits or hyphens, one label without a dot, not starting or ending with a hyphen. Example: paypal
`pattern`	No	Wildcard search instead of keyword: '' matches any characters and '?' exactly one, at most 2 wildcards, at least 5 other characters including 3 in a row, 63 in total. Example: payp?l
`fetchSize`	No	Subdomains per page, 1 to 10000. Default: 100
`pageToken`	No	nextPageToken from the previous result, to get the next page. Pass the same keyword or pattern with it.

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 13, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Beyond the readOnly/openWorld/idempotent annotations, the description discloses credit cost (5 credits per page), the upstream WhoisFreaks API key mechanism, that the caller's account credits are consumed, and concrete failure modes with HTTP codes. It also spells out pagination via nextPageToken and the returned fields, which the annotations alone do not cover.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is long but organized: purpose first, then routing to siblings, then cost, return shape, pagination, and error behavior. Nearly every sentence carries distinct information, though the error-code enumeration is slightly verbose for a description that could be summarized.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 4-parameter read-only search tool with no output schema, the description covers cost, auth, pagination, return fields, and failure handling. Nothing an agent needs to call it correctly or interpret empty/failed results is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3, but the description adds a constraint the schema does not encode: exactly one of keyword or pattern must be supplied (the schema marks nothing required and has no exclusivity rule). The pageToken reuse instruction (pass it with the same keyword or pattern) also adds meaning beyond the schema field text.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb and resource (find subdomains containing a typo variant of a brand or matching a wildcard) and illustrates it with a concrete example, login.paypa1.example.com. It also explicitly distinguishes itself from domainDiscovery and subdomainLookup, so an agent can route between them without opening the schemas.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It states the phishing/brand-protection use case, the mutually exclusive input rule (exactly one of keyword or pattern), and names the alternatives for adjacent needs: subdomainLookup for the subdomains of one domain, domainReputation for judging risk. This is explicit when-to-use and when-to-use-something-else guidance.

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

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