Domain Intelligence
FreeConduct passive OSINT for domains effortlessly.
Free · Opens the source repo
What Domain Intelligence does
Domain Intelligence is a powerful skill designed for passive reconnaissance of domain-related information, utilizing only the Python standard library. It operates seamlessly across Linux, macOS, and Windows without any external dependencies or API keys. This makes it an ideal tool for developers and security professionals looking to gather insights on domains without the need for complex setups or configurations.
The skill comes with a command-line interface through the domain_intel.py script, which allows users to perform a variety of operations. You can discover subdomains using Certificate Transparency logs, inspect SSL certificates for expiry and issuer details, perform WHOIS lookups to retrieve registration information, and query DNS records for various types. Additionally, it can check domain availability through a combination of passive signals from WHOIS and DNS, making it a versatile tool for domain analysis.
This skill is particularly beneficial for those in cybersecurity, IT operations, or any field requiring domain intelligence. It simplifies the process of gathering important data points about domains, which can be crucial for security assessments, research, or even competitive analysis. The structured JSON output format ensures that the results are easy to parse and integrate into other workflows or tools.
However, users should be aware that while the skill provides a wealth of information, it does not perform active scanning or vulnerability testing, which may be necessary for more in-depth security assessments. For users looking for a straightforward and efficient way to gather domain intelligence without the overhead of additional tools or services, Domain Intelligence is a solid choice.
When to use it
Use this skill when you need to gather information about domains, such as subdomains, SSL certificates, WHOIS data, and DNS records, without active probing.
When not to use it
This skill is not suitable for active vulnerability assessments or when real-time data from APIs is required.
What you can build with it
Subdomain Discovery
Use the subdomain command to find subdomains associated with a domain from Certificate Transparency logs.
SSL Certificate Inspection
Check the details of an SSL certificate, including expiry dates and issuer information, with a simple command.
WHOIS Lookup
Retrieve registration details for a domain, including registrar and important dates, using the WHOIS command.
How to install Domain Intelligence
View source1. Install with the skills CLI
npx skills add nousresearch/hermes-agent/domain-intel --agent claude-code2. Or install it manually
Download the skill folder and drop it into ~/.claude/skills/ for all projects, or .claude/skills/ to scope it to one repo. Restart Claude Code so it picks up the new skill.
Anthropic's agentic coding CLI, and the reference implementation of Agent Skills. Drop a skill folder into ~/.claude/skills and Claude Code loads it automatically whenever a task matches the skill's description. Claude Code docs
Inside SKILL.md
Written by nousresearchDomain Intelligence — Passive OSINT
Passive domain reconnaissance using only Python stdlib. Zero dependencies. Zero API keys. Works on Linux, macOS, and Windows.
Helper script
This skill includes scripts/domain_intel.py — a complete CLI tool for all domain intelligence operations.
# Subdomain discovery via Certificate Transparency logs
python3 SKILL_DIR/scripts/domain_intel.py subdomains example.com
# SSL certificate inspection (expiry, cipher, SANs, issuer)
python3 SKILL_DIR/scripts/domain_intel.py ssl example.com
# WHOIS lookup (registrar, dates, name servers — 100+ TLDs)
python3 SKILL_DIR/scripts/domain_intel.py whois example.com
# DNS records (A, AAAA, MX, NS, TXT, CNAME)
python3 SKILL_DIR/scripts/domain_intel.py dns example.com
# Domain availability check (passive: DNS + WHOIS + SSL signals)
python3 SKILL_DIR/scripts/domain_intel.py available coolstartup.io
# Bulk analysis — multiple domains, multiple checks in parallel
python3 SKILL_DIR/scripts/domain_intel.py bulk example.com github.com google.com
python3 SKILL_DIR/scripts/domain_intel.py bulk example.com github.com --checks ssl,dns
SKILL_DIR is the directory containing this SKILL.md file. All output is structured JSON.
Available commands
| Command | What it does | Data source |
|---|---|---|
subdomains | Find subdomains from certificate logs | crt.sh (HTTPS) |
ssl | Inspect TLS certificate details | Direct TCP:443 to target |
whois | Registration info, registrar, dates | WHOIS servers (TCP:43) |
dns | A, AAAA, MX, NS, TXT, CNAME records | System DNS + Google DoH |
available | Check if domain is registered | DNS + WHOIS + SSL signals |
bulk | Run multiple checks on multiple domains | All of the above |
When to use this vs built-in tools
- Use this skill for infrastructure questions: subdomains, SSL certs, WHOIS, DNS records, availability
- Use
web_searchfor general research about what a domain/company does - Use
web_extractto get the actual content of a webpage - Use
terminalwithcurl -Ifor a simple "is this URL reachable" check
| Task | Better tool | Why |
|---|---|---|
| "What does example.com do?" | web_extract | Gets page content, not DNS/WHOIS data |
| "Find info about a company" | web_search | General research, not domain-specific |
| "Is this website safe?" | web_search | Reputation checks need web context |
| "Check if a URL is reachable" | terminal with curl -I | Simple HTTP check |
| "Find subdomains of X" | This skill | Only passive source for this |
| "When does the SSL cert expire?" | This skill | Built-in tools can't inspect TLS |
| "Who registered this domain?" | This skill | WHOIS data not in web search |
| "Is coolstartup.io available?" | This skill | Passive availability via DNS+WHOIS+SSL |
Platform compatibility
Pure Python stdlib (socket, ssl, urllib, json, concurrent.futures).
Works identically on Linux, macOS, and Windows with no dependencies.
- crt.sh queries use HTTPS (port 443) — works behind most firewalls
- WHOIS queries use TCP port 43 — may be blocked on restrictive networks
- DNS queries use Google DoH (HTTPS) for MX/NS/TXT — firewall-friendly
- SSL checks connect to the target on port 443 — the only "active" operation
Data sources
All queries are passive — no port scanning, no vulnerability testing:
- crt.sh — Certificate Transparency logs (subdomain discovery, HTTPS only)
- WHOIS servers — Direct TCP to 100+ authoritative TLD registrars
- Google DNS-over-HTTPS — MX, NS, TXT, CNAME resolution (firewall-friendly)
- System DNS — A/AAAA record resolution
- SSL check is the only "active" operation (TCP connection to target:443)
Notes
- WHOIS queries use TCP port 43 — may be blocked on restrictive networks
- Some WHOIS servers redact registrant info (GDPR) — mention this to the user
- crt.sh can be slow for very popular domains (thousands of certs) — set reasonable expectations
- The availability check is heuristic-based (3 passive signals) — not authoritative like a registrar API
Contributed by @FurkanL0
Frequently asked questions about Domain Intelligence
Similar skills
GitHub Actions Hardening
Enhance the security of your GitHub Actions workflows.
Sensitive Logging Audit
Audit and fix sensitive data exposure in Python logging.
Android App Static Analysis
Automate security assessments of Android apps with MobSF.
Integrating DAST with OWASP ZAP
Seamlessly integrate dynamic security testing into CI/CD pipelines.
Implementing Runtime Security with Tetragon
Enhance Kubernetes security with eBPF-based observability.
Implementing Mobile Application Management
Secure enterprise data on mobile devices with app-level controls.