censys-api

censys-api is a skill for Claude Code from Liberty91LTD/cti-skills. It costs 19 tokens per session (664 once invoked), scanned A, original, MIT.

A reference for the Censys API, a service that provides information about internet-facing hosts and their certificates. It covers authentication, search requests, host details, TLS certificates, and usage limits.

In plain words
What is it for?
Use it for host reconnaissance, certificate lookups, service and port checks, network ownership details, and geographic or operating-system information.
Why use it?
It gives agents the exact request patterns and data fields needed to investigate hosts without guessing how the service works.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Good fit Use it for host reconnaissance, certificate lookups, service and port checks, network ownership details, and geographic or operating-system information.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/liberty91ltd/cti-skills/censys-api
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add Liberty91LTD/cti-skills --skill censys-api
Clone the repo
git clone --depth 1 https://github.com/Liberty91LTD/cti-skills

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for censys-api

README.md
[![agentmods](https://agentmods.dev/badge/skills/liberty91ltd/cti-skills/censys-api/github.svg)](https://agentmods.dev/skills/liberty91ltd/cti-skills/censys-api)
Your own site
<a href="https://agentmods.dev/skills/liberty91ltd/cti-skills/censys-api"><img src="https://agentmods.dev/badge/skills/liberty91ltd/cti-skills/censys-api/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for censys-api

Your own site · 80×15
<a href="https://agentmods.dev/skills/liberty91ltd/cti-skills/censys-api"><img src="https://agentmods.dev/badge/skills/liberty91ltd/cti-skills/censys-api.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 19 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 664 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00019 $0.00664
Opus 5 $0.00010 $0.00332
Sonnet 5 $0.00004 $0.00133
Haiku 4.5 $0.00002 $0.00066

Measured 12d ago against content hash 36b6b333d058, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

censys-api scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s "https://search.censys.io/api/v2/hosts/{ip}" \
skills/censys-api/SKILL.md · 90 lines

How it starts

The opening of the file, as written. The whole thing — 90 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Censys API v2

Base URL

https://search.censys.io/api/v2

Authentication

Basic Auth: $CENSYS_API_ID:$CENSYS_API_SECRET

curl -s "https://search.censys.io/api/v2/hosts/{ip}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"

Rate Limits

  • Free: 250 queries/month, 5 results/query
  • Paid: Higher limits based on plan

Important: Free tier is very limited. Use selectively — prioritise high-value lookups.

Key Endpoints

View Host

curl -s "https://search.censys.io/api/v2/hosts/{ip}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"

Useful fields:

  • result.services[] — port, service_name, transport_protocol, banner
  • result.services[].tls.certificates — TLS certificate chain
  • result.autonomous_system — ASN info
  • result.location — geographic location
  • result.operating_system — OS detection
  • result.last_updated_at — scan freshness

Search Hosts

curl -s "https://search.censys.io/api/v2/hosts/search?q={query}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"

Search syntax: services.port: 443 AND services.tls.certificates.leaf_data.subject.common_name: example.com

View Certificate

curl -s "https://search.censys.io/api/v2/certificates/{fingerprint}" \
  -u "$CENSYS_API_ID:$CENSYS_API_SECRET"

Common Search Queries

  • ip: {ip} — specific host
  • services.tls.certificates.leaf_data.subject.common_name: {domain} — hosts with cert for domain
  • services.http.response.body_hash: {hash} — hosts serving same content
  • services.jarm.fingerprint: {jarm} — hosts with same JARM fingerprint (C2 detection)
  • labels: {label} — Censys-labeled hosts

CTI Value

Censys excels at:

  • Certificate transparency analysis (finding related infrastructure)
  • JARM fingerprinting (identifying C2 frameworks)
  • Service banner analysis
  • Historical infrastructure changes

Response Summary Format

ip: <IP>
services:
  - port: <port>
    service: <name>
    banner: <truncated>
certificates:
  - subject_cn: <common name>
    issuer: <issuer>
    valid_from: <date>
    valid_to: <date>
autonomous_system:
  asn: <number>
  name: <name>
location:
  country: <country>
  city: <city>
last_updated: <date>

Read the full file on GitHub · 90 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 12d ago First seen · 90 lines · 19 tokens per session scan A 36b6b333d058

Subscribe to this mod's changes

censys-api is a skill published in the GitHub repository Liberty91LTD/cti-skills (18 stars, last pushed 1mo ago), licensed MIT. It adds 19 tokens to every session and 664 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.