CertIndex MCP

official

The only certificate-transparency MCP server. Search 2.15B+ TLS certificates, monitor domains for new issuance, stream the global CT firehose to your agent.

GitHub

What can you do with CertIndex MCP?

Search certificates by domain or issuer — Find TLS certificates matching a domain, CN, issuer, or SAN pattern using search_certificates.
Retrieve a certificate by fingerprint — Fetch full PEM data and CT log metadata for a specific SHA-256 fingerprint with get_certificate.
List all certificates for a domain — Get every certificate ever issued for an exact domain via get_domain_certificates, optionally filtered to currently valid certs only.
Enumerate subdomains seen in CT logs — Discover unique subdomains observed for a domain using cursor-based pagination in get_subdomains.
Find certificates expiring soon — Identify certificates for a domain that expire within a given number of days using get_expiring_certs.
Run a global index sweep — Submit an async substring search across the entire CT corpus by CN or SAN with submit_global_sweep, then poll results with get_sweep_results.

Documentation

certindex-mcp

An MCP (Model Context Protocol) server that exposes CertIndex's Certificate Transparency search tools to any MCP-compatible client (Claude Desktop, the MCP Inspector, Continue, etc.).

CertIndex indexes the full public CT corpus (~5 M certificates, growing ~100 k/day). This server wraps the public CertIndex REST API so an LLM can ask questions like:

"List every TLS certificate ever issued for example.com."
"What subdomains has Let's Encrypt seen for mycompany.io?"
"Show me certs expiring in the next 30 days for api.mycompany.io."
"Pull the full PEM and CT log metadata for SHA-256 <fingerprint>."

Why this repo exists

The CertIndex monorepo bundles an MCP server (mounted at https://api.ctindex.io/mcp) that talks directly to the production Postgres index. This standalone package is a thin client-side shim: it speaks MCP to your editor / agent and forwards every tool call to the hosted CertIndex REST API over HTTPS. Two consequences:

You don't need a copy of the index — sign up for a free API key at https://ctindex.io and you're done.
The package has a tiny dependency footprint (mcp, httpx, pydantic) — easy to audit, easy to vendor, no DB drivers.

Install

pip install certindex-mcp

Or with uvx for one-shot use:

uvx certindex-mcp

To install the latest development version from source instead:

pip install git+https://github.com/certindex/certindex-mcp

Quickstart — Claude Desktop

Add to ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or %APPDATA%\Claude\claude_desktop_config.json (Windows):

{
  "mcpServers": {
    "certindex": {
      "command": "uvx",
      "args": ["certindex-mcp"],
      "env": {
        "CERTINDEX_API_KEY": "ctx_live_..."
      }
    }
  }
}

Restart Claude Desktop. The ten CertIndex tools appear in the tool tray.

Tools

Ten tools, matching the hosted CertIndex MCP server 1:1:

Tool	What it does	Notable parameters
`search_certificates`	Search the CT index by domain, CN, issuer, SAN, validity, or wildcard status.	`domain`, `cn`, `issuer`, `san`, `expired`, `is_wildcard`, `page`/`limit`
`get_certificate`	Fetch a single cert by SHA-256 fingerprint.	`sha256`, `include_enrichment`
`get_domain_certificates`	Every cert ever issued for an exact domain.	`valid_only`, `include_enrichment`, `include_signals` (paid plans), `page`/`limit`
`get_subdomains`	Enumerate unique subdomains seen in CT.	Offset (`page`/`limit`) or keyset cursor mode — pass `cursor=""` to start, then feed back each response's `next_cursor`
`get_latest_cert`	Most recent currently-valid cert for a domain.	`include_enrichment`, `include_signals`, `include_precerts` (let precertificates compete for "latest")
`get_expiring_certs`	Certs for a domain expiring within `days` days.	`days`
`submit_global_sweep`	Submit an async, domain-less CN/SAN substring sweep of the entire index (`POST /v1/sweeps`).	`cn`/`san_contains` (3+ chars, at least one required), `issuer`, `is_wildcard`, `is_precert`, `expired`, `first_seen_`/`not_after_` date bounds, `strict_attribution`, `resume_token` (continuation past the result cap)
`get_sweep_results`	Poll a sweep job and paginate its results when done (`GET /v1/sweeps/{id}`).	`sweep_id`, `page`/`limit` (up to 1,000)
`get_usage`	Caller's tier, current usage, remaining quota, and entitlements.	—
`get_historical_backfill_status`	Check / start the paid deep-history backfill for a domain.	`domain`

Quickstart — MCP Inspector

export CERTINDEX_API_KEY=ctx_live_...
npx @modelcontextprotocol/inspector uvx certindex-mcp

Configuration

Env var	Default	Description
`CERTINDEX_API_KEY`	(required)	Your CertIndex API key. Mint one at https://ctindex.io/app/keys
`CERTINDEX_BASE_URL`	`https://api.ctindex.io`	Override for self-hosted deployments / staging
`CERTINDEX_TIMEOUT`	`30`	Per-request HTTP timeout (seconds)

Security

Input validation, rate-limit handling, and our supply-chain posture are documented in SECURITY.md. Please report vulnerabilities to security@ctindex.io rather than filing public issues.

Development

git clone https://github.com/certindex/certindex-mcp
cd certindex-mcp
pip install -e ".[dev]"
pytest

CI runs on Python 3.11 / 3.12 / 3.13.