# Lookproof IP-in-CIDR Containment Check

> Lookproof IP-in-CIDR Containment Check is a paid API for AI agents from api.lookproof.dev, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-31).

Checks whether a single IPv4 or IPv6 address falls within any of up to 100 CIDR blocks, returning per-block match results and the list of matching blocks.

## Facts

- Endpoint: POST https://api.lookproof.dev/v1/ip/contains?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/lookproof-ip-in-cidr-containment-check-9165aa10
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_VGglXcltiB5sv31CPyj7-

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability lookproof-ip-in-cidr-containment-check-9165aa10 -d '<json body>'
```

Example prompt: Check whether 192.0.2.10 is contained in any of these CIDR blocks: 192.0.2.0/24, 10.0.0.0/8, and 172.16.0.0/12 — and tell me which ones match.

## When to prefer this

Use this endpoint when an agent needs to perform offline, server-side IP containment checks against multiple CIDR ranges in a single call — especially for allow/deny list enforcement, SPF record validation, or cloud provider IP attribution. Prefer it over client-side logic when auditable, consistent, and multi-block batch evaluation is needed without managing networking libraries.

## Known failure modes

- Invalid IP address format returns a validation error
- Malformed CIDR notation in the list causes an error response
- Submitting more than 100 CIDRs exceeds the maxItems limit and is rejected
- Mixing an IPv6 input with IPv4 CIDRs yields no matches (by design, not an error)
- Empty CIDR array rejected due to minItems constraint

## How this service works

Check SPF, DMARC, DKIM, MTA-STS, DNSSEC and more, with results that explain what was found and why. Free browser checks and a pay-per-request API with x402.

## Output

Returns a boolean result for each submitted CIDR block indicating whether it contains the input IP address, plus a filtered list of only the blocks that matched. Blocks of the opposite IP version (e.g. IPv4 CIDRs when the input is IPv6) are automatically treated as non-matching.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "ip": {
   "type": "string",
   "title": "Ip",
   "maxLength": 64,
   "minLength": 2
  },
  "cidrs": {
   "type": "array",
   "items": {
    "type": "string",
    "maxLength": 64,
    "minLength": 2
   },
   "title": "Cidrs",
   "maxItems": 100,
   "minItems": 1
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/lookproof-ip-in-cidr-containment-check-9165aa10/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.lookproof.dev](https://www.zero.xyz/host/api.lookproof.dev/llms.txt)