Clearfront MCP Server

search_crt

Enumerate subdomains from certificate transparency logs to discover internal and staging hosts that do not resolve publicly.

Instructions

Enumerate subdomains from certificate transparency logs via crt.sh. Keyless and purely passive (public CA logs), surfaces internal/staging hosts that never resolve publicly. Authorized use only: your own assets or a target you are authorized to assess. Passive, public-source collection.

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": "search_crt"
  }
}

Input Schema

Name	Required	Description	Default
`domain`	Yes
`json_output`	No	Return result as structured JSON.

Schema Changelog

Changes observed during successful MCP inspections.

Addedv2.7.2Jul 27, 2026
Removedv2.7.2Jul 27, 2026
First observedv2.5.0Jul 8, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Describes behavior as passive, keyless, and using public CA logs, which is sufficient for a non-destructive tool. No annotations provided, so description carries weight. Lacks details on rate limits or output size, but core behavioral traits are disclosed.

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?

Three sentences, front-loaded with purpose, then usage and behavioral notes. No unnecessary words, but could be more structured by separating guidelines from behavioral traits. Still concise and efficient.

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?

Lacks details on return format, pagination, or limits. No output schema provided. While common knowledge for crt.sh, a newer AI agent might benefit from knowing whether results are truncated or how to handle large outputs. Adequate but not complete.

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

Parameters2/5

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

Description does not elaborate on parameter semantics. Schema describes json_output but not domain. The description adds no meaning beyond the schema; e.g., it doesn't specify domain format or constraints. Schema coverage is 50%, and description fails to compensate.

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?

Clearly states it enumerates subdomains via crt.sh certificate transparency logs. This is a specific verb and resource, distinguishing it from sibling tools like search_dns or search_censys which use different data sources.

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?

Provides explicit guidance: keyless, passive, public-source collection, and authorized use only. It surfaces non-resolving internal/staging hosts, implying use for passive reconnaissance. Does not explicitly mention when to avoid or alternatives, but context is clear.

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