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.

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What can you do with CertIndex MCP?

Search certificate transparency data — Ask for TLS certificates indexed for a domain, CN, issuer, SAN, or wildcard status via search_certificates.
Fetch certificate details — Retrieve a single certificate's full PEM and CT log metadata by SHA-256 fingerprint using get_certificate.
Enumerate subdomains — List unique subdomains seen in CT for a domain, with cursor-based pagination via get_subdomains.
Monitor certificate expiry — Find certificates expiring within a specified number of days for a domain using get_expiring_certs.
Run global sweeps — Submit async substring sweeps across the entire index for CN/SAN patterns via submit_global_sweep, then poll results with get_sweep_results.
Check API usage — Review your tier, current usage, remaining quota, and entitlements with get_usage.

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 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:

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

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.