Crtsh MCP Server

@pipeworx/crtsh

Certificate Transparency log search from crt.sh — every TLS certificate ever issued for a domain and its subdomains, with issuer, validity window, serial number and the full SAN list.

Part of Pipeworx — an MCP gateway connecting AI agents to 1863+ live data sources. This is an independent, unofficial integration — not affiliated with, endorsed by, or published by the upstream provider.

Tools

• crtsh_search_domain(domain, include_subdomains?, exclude_expired?, limit?) — every logged certificate for a domain, de-duplicated by certificate id and sorted newest-first, plus unique_names: every distinct hostname seen across all of them. That list is the subdomain-enumeration answer most callers actually want.
• crtsh_certificate(id?, serial?, include_pem?) — one certificate by crt.sh id or by hex serial number. Returns the PEM body; a lookup by serial also carries the logged metadata, a lookup by id returns the PEM alone (see Traps).

Auth

Keyless.

Data sources

• https://crt.sh/?q=%25.example.com&output=json — certificate search by identity (domain, SAN, or %-wildcard).
• https://crt.sh/?serial=...&output=json — certificate search by hex serial.
• <https://crt.sh/?d=> — the PEM body of one certificate.

crt.sh is operated by Sectigo and is a JSON view over a PostgreSQL database of the public Certificate Transparency logs.

Traps

• crt.sh is slow. A wildcard query on a large domain routinely takes 10-20s and the server enforces no query timeout of its own. Every call in this pack is bound at 25s rather than the pack default.
• output=json is honoured only for identity-style queries — q=, serial=, Identity=. ?id=<n>&output=json answers the literal string Unsupported output type: json with HTTP 200. Parsed without checking, that is a silent zero; crtJson() rejects any body that does not start with [ or {.
• ?d=<id> and ?id=<id> are different parameters. d returns the PEM; id renders an HTML page. This is why crtsh_certificate can return the PEM for an id but not its metadata — there is no JSON-by-id endpoint, so metadata arrives only on the serial= path.
• name_value packs every SAN into one newline-separated field. Splitting it is the difference between reporting 8 certificates and the 40 hostnames the caller asked for.
• One certificate appears as several rows — crt.sh returns one row per (certificate, matching identity), so a cert with six matching SANs is six rows with the same id. De-duplicate by id or every count is inflated.
• A precertificate and its final certificate are two CT entries with two crt.sh ids and the same serial number, so an id count roughly doubles the number of certificates actually issued. crtsh_search_domain reports both: total_log_entries_found (distinct crt.sh ids) and unique_certificates_found (distinct serials). Quote the second one when answering "how many certificates".
• CT covers publicly trusted CAs only. A host behind an internal or private CA appears nowhere here; an empty result is not proof the host does not exist.

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "crtsh": {
      "url": "https://gateway.pipeworx.io/crtsh/mcp"
    }
  }
}

What this endpoint actually serves

tools/list at https://gateway.pipeworx.io/crtsh/mcp returns the tools in the table above plus the shared Pipeworx meta-tools — ask_pipeworx, discover_tools, search_within, remember/recall and the rest of the gateway-wide set. So the tool count you see is larger than this table: a single-pack endpoint currently lists roughly 30 shared tools alongside the pack's own. The connection's initialize response states its exact scope, and is the authoritative answer for a given day.

This is deliberate, not multiplexing by accident. The meta-tools are what let a scoped connection answer a question this pack does not cover — via ask_pipeworx, which routes across the whole catalog — without you adding a second MCP server. There is currently no way to mount a pack endpoint without them; if the extra schemas cost you more context than the routing is worth, connect to the full gateway once rather than to several pack endpoints.

Or connect to the full Pipeworx gateway to get every pack's tools listed directly, instead of just this one's:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Both URLs reach the same gateway and the same 1863+ data sources. The only difference is which pack's tools are listed directly; ask_pipeworx reaches all of them from either one.

No MCP client? Call it over HTTP

curl -X POST https://gateway.pipeworx.io/v1/tools/crtsh_search_domain \
  -H 'Content-Type: application/json' \
  -d '{"domain":"pipeworx.io","exclude_expired":true,"limit":3}'

No account needed for the first calls. Inspect any tool: GET https://gateway.pipeworx.io/v1/tools/crtsh_search_domain. Find one: POST https://gateway.pipeworx.io/v1/tools/search_packs with {"query":"..."}.

Run it from npm

@pipeworx/mcp-crtsh is a local stdio bridge to the Pipeworx gateway: your MCP client starts it with npx, and it forwards every call to the same https://gateway.pipeworx.io/crtsh/mcp endpoint shown above. It needs network access; there is no offline mode.

{
  "mcpServers": {
    "crtsh": {
      "command": "npx",
      "args": ["-y", "@pipeworx/mcp-crtsh"]
    }
  }
}

Without a key it calls anonymously, capped at 50 calls a day. A free account raises that to 200 a day: get a key at https://pipeworx.io/signup and add "env": { "PIPEWORX_API_KEY": "<your key>" } to the server entry. The key is sent as a Bearer token, the same way a hosted connection sends it, so calls are metered and billed exactly as they are there.

It lists only this pack's tools by default. Set PIPEWORX_META_TOOLS=1 to also list ask_pipeworx and the other gateway-wide tools.

Behind an HTTPS proxy: Node's built-in fetch does not read HTTPS_PROXY by default. Newer Node releases honour it when NODE_USE_ENV_PROXY=1 is set; check your Node version's documentation.

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English — this works on the pack endpoint above as well as on the full gateway:

ask_pipeworx({ question: "your question about Crtsh data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides
• pipeworx.io

License

MIT