MoonMCP

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enumerate_subdomains

Passively discover subdomains of any domain using multiple free OSINT sources in parallel, without sending traffic to the target.

Instructions

Passively enumerate subdomains of a domain via free OSINT sources.

Queries certificate transparency (crt.sh), HackerTarget, AnubisDB and AlienVault OTX in parallel and merges the results. Passive — no packets are sent to the target itself. sources optionally restricts which providers to use (see server_status / available list: crtsh, hackertarget, anubis, otx).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "domain": "<domain>"
    },
    "name": "enumerate_subdomains"
  }
}

Input Schema

Name	Required	Description	Default
`domain`	Yes
`sources`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jul 8, 2026

TDQS

A4.3/5.0

Behavior4/5

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

With no annotations provided, the description discloses key behavioral traits: it is passive (no packets sent), queries multiple sources in parallel, merges results, and allows source restriction. It does not mention rate limits or data freshness, but for a read-only tool the disclosure is sufficient.

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

Conciseness5/5

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

The description is concise with three focused sentences, front-loading the core purpose. No superfluous words, and the information is well-structured for quick parsing.

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

Completeness3/5

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

While the description covers purpose, parameters, and behavior, it lacks output details (e.g., format of results, additional metadata) and does not mention authentication requirements. Given no output schema, this missing information reduces completeness for an agent expecting to process results.

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?

The description adds meaning beyond the schema by explaining the `sources` parameter's purpose (restrict providers) and referencing `server_status` for available options. Although the schema has 0% description coverage, the description compensates well for both parameters.

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 clearly states the specific verb 'enumerate subdomains' and the resource 'domain', and distinguishes it from sibling reconnaissance tools by specifying it is passive and uses OSINT sources. This makes the tool's purpose immediately clear and distinct.

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

Usage Guidelines4/5

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 (passive subdomain enumeration) and mentions optional provider restriction. However, it does not explicitly state when not to use it or suggest alternative tools for active enumeration, though this is implied.

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