osint-mcp-server

st_subdomains

Enumerate subdomains for a domain via SecurityTrails to uncover hidden assets and map attack surface.

Instructions

Enumerate subdomains for a domain via SecurityTrails. Returns FQDNs. Requires ST_API_KEY.

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": "st_subdomains"
  }
}

Input Schema

Name	Required	Description	Default
`domain`	Yes	Domain to enumerate subdomains for

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.2.0Mar 17, 2026

TDQS

A3.8/5.0

Behavior3/5

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

No annotations are provided, so the description must cover behavioral aspects. It mentions the external data source (SecurityTrails) and returned format (FQDNs), but omits details like rate limits, authentication method, or whether it is a read-only operation. Basic transparency is adequate but not comprehensive.

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 extremely concise: three sentences that convey purpose, return type, and requirement. No fluff or redundant information.

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

Completeness4/5

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

For a simple tool with one parameter and no output schema, the description is largely complete. It covers what, returns, and requirement. However, given the context of many sibling tools, adding a brief note on data source uniqueness would improve completeness.

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

Parameters3/5

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

The schema provides 100% coverage with description for the 'domain' parameter. The tool description does not add meaningful extra semantics beyond the schema, so the baseline score of 3 is appropriate.

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 tool enumerates subdomains for a domain via SecurityTrails and returns FQDNs. The verb 'enumerate' and resource 'subdomains for a domain' are specific, and it is easily distinguished from sibling tools like vt_subdomains or dns_lookup.

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

Usage Guidelines3/5

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

The description mentions 'Requires ST_API_KEY' as a prerequisite, but does not provide guidance on when to use this tool versus alternatives (e.g., crtsh_search, vt_subdomains). Given 35+ sibling tools, more explicit selection criteria would be beneficial.

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