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Crtsh

by io.github.pipeworx-io
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Crtsh Search Domain

crtsh_search_domain
Read-onlyIdempotent

"Find subdomains of [domain]" / "what TLS certificates exist for [domain]" / "certificate transparency for [host]" / "who issued the cert for [site]" — every certificate ever logged to the public Certificate Transparency logs for a domain and (by default) its subdomains, from crt.sh. AUTHORITATIVE for subdomain discovery and certificate inventory: CAs are required to log every certificate they issue, so this finds hosts that appear in no DNS zone transfer and no web crawl. Returns issuer, validity window, serial number and the full SAN list per certificate, plus a de-duplicated list of every hostname seen. PREFER OVER WEB SEARCH for "what hostnames does this organisation have" and for spotting mis-issued or forgotten certificates.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "limit": 3,
      "domain": "pipeworx.io",
      "exclude_expired": true
    },
    "name": "crtsh_search_domain"
  }
}

Input Schema

NameRequiredDescriptionDefault
limitNoMaximum certificates to return, 1-1000. Default 100. crt.sh returns newest-first once sorted here.
domainYesDomain to search, e.g. "cloudflare.com". Do not include a scheme or a leading wildcard.
exclude_expiredNoReturn only certificates that have not passed their notAfter date. Default false (full history).
include_subdomainsNoSearch "%.domain" (every subdomain) as well as the domain itself. Default true.

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.2/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: it explains that CAs are required to log every issued certificate, that the search covers certificates logged for the domain and by default its subdomains, and that it returns issuer, validity window, serial number, full SAN list, and a de-duplicated hostname list. It does not discuss rate limits, authentication, or error behavior, which keeps it from a 5.

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 front-loaded with example user questions before explaining the core capability, which is slightly noisy but useful for query recognition. Every sentence contributes to purpose, authority, return content, or usage preference, with no obvious filler. It is appropriately sized for a tool of this scope.

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?

There is no output schema, so the description carries the burden of explaining what is returned, and it does so clearly by naming issuer, validity window, serial number, SAN list, and a de-duplicated hostname list. Annotations cover the safety profile and the input schema fully documents all parameters, so the description is complete enough for an agent to invoke the tool correctly.

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?

Schema description coverage is 100%, so the input schema already documents all four parameters, including domain format, limit range, exclude_expired default, and include_subdomains default. The description does not add syntax or constraints beyond the schema, so the baseline of 3 applies.

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: it finds every certificate ever logged to Certificate Transparency logs for a domain and its subdomains, and explicitly says it is AUTHORITATIVE for subdomain discovery and certificate inventory. It distinguishes the tool from web search by saying to PREFER OVER WEB SEARCH for discovering an organisation's hostnames. This is enough for an agent to identify the tool's core purpose without opening the schema.

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 states when to use it, such as for 'what hostnames does this organisation have' and for spotting mis-issued or forgotten certificates, and explicitly says to prefer it over web search for those tasks. It does not mention when to choose the sibling crtsh_certificate tool or when this tool is not appropriate, so the guidance is clear but not fully exhaustive.

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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