# IP Blocklist Check (DNSBL)

> IP Blocklist Check (DNSBL) is a paid API for AI agents from flat-rate-llm.kikoribera03.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Checks a single IPv4 address against nine public DNS blocklists simultaneously and returns each list's result code, reason text, and delisting URL.

## Facts

- Endpoint: POST https://flat-rate-llm.kikoribera03.workers.dev/v1/red/dnsbl
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/ip-blocklist-check-dnsbl-13fc8607
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0cPbAdXWT7SDbvAjL4Uqf

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 ip-blocklist-check-dnsbl-13fc8607 -d '<json body>'
```

Example prompt: Check if the IP address 203.0.113.42 is listed on any DNS blocklists — I need to know which lists it appears on, what reason each list gives, and where I can request delisting.

## When to prefer this

Choose this endpoint when you need authoritative, per-list DNSBL results with raw return codes and reason text rather than an aggregated reputation score. It is ideal for debugging email deliverability, investigating spam complaints, or verifying an IP before using it for outbound mail. The built-in liveness check per list prevents false 'clean' readings from dead blocklists, making it more reliable than naive DNSBL lookups. Prefer it over general IP reputation APIs when you need the actual delisting URLs and list-specific reason strings.

## Known failure modes

- A specific blocklist is unreachable or refuses queries — returned as 'unavailable' rather than clean, preventing false negatives
- Invalid IPv4 address input may return an error or unexpected results
- IPv6 addresses are not supported — only IPv4
- Network timeouts reaching individual DNSBL servers may cause some lists to show as unavailable

## How this service works

60 paid endpoints with no metering, no API key and no account. Each endpoint has one flat price per call, whatever the size of the request: LLM completions with automatic failover across several large models, read-only EVM tooling over Base, Ethereum, Polygon, Arbitrum and Optimism, and pure crypto utilities that touch no network.

## Output

For each of the nine DNS blocklists checked, the agent receives: the list name, whether the list was reachable and functional (confirmed via RFC 5782 test entry), the raw return code if the IP is listed, the human-readable reason text published by that list, and a delisting URL for any hits. Lists that are down or refusing queries are explicitly marked as unavailable rather than reported as clean.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "ip"
 ],
 "properties": {
  "ip": {
   "type": "string",
   "description": "The IPv4 address to check. IPv6 is not accepted: these nine lists are IPv4 zones."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "ip": {
   "type": "string"
  },
  "listed": {
   "type": "boolean"
  },
  "results": {
   "type": "array",
   "items": {
    "type": "object"
   }
  },
  "listedOn": {
   "type": "array",
   "items": {
    "type": "object"
   }
  },
  "listedCount": {
   "type": "number"
  },
  "listsQueried": {
   "type": "number"
  },
  "listsAvailable": {
   "type": "number"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/ip-blocklist-check-dnsbl-13fc8607/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from flat-rate-llm.kikoribera03.workers.dev](https://www.zero.xyz/host/flat-rate-llm.kikoribera03.workers.dev/llms.txt)