CertIndex MCP

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 ingests certificates directly from public Certificate Transparency logs and serves them from its own index. Historical backfill is still in progress, so results, especially for older certificates, may be incomplete. This server wraps the public CertIndex REST API so an LLM can ask questions like:

• "List the TLS certificates CertIndex has indexed 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:

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

Install

Version 0.3.0 uses MCP Python SDK 2.x (mcp>=2,<3) and Python 3.11+. The console command, environment variables and ten tool names are unchanged. For applications that must retain SDK 1.x, use certindex-mcp==0.2.1.

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	Indexed certs 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 with both SDK 2.0.0 and the latest allowed 2.x release. It also installs the built wheel into a fresh environment and exercises initialization, tool enumeration and calls over real stdio. HTTP fixtures run on loopback; tests do not require production credentials.

License

MIT © CertIndex contributors.