# Base Sequencer Pending Transaction Feed (Mempool Scanner)

> Base Sequencer Pending Transaction Feed (Mempool Scanner) is a paid API for AI agents from httpay.xyz, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-13).

Returns the Base sequencer's pending transaction queue filtered for large pending swaps, MEV opportunities, and frontrunning signals

## Facts

- Endpoint: POST https://httpay.xyz/api/mempool-scanner
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/httpay-xyz-d2bdc836
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_-2KkEMZxqrpN05rMn0Y14

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 httpay-xyz-d2bdc836 -d '<json body>'
```

Example prompt: Show me the current Base sequencer pending transaction queue — I want to see large pending swaps and any MEV sandwich or frontrunning opportunities available right now.

## When to prefer this

Use this endpoint when you need real-time visibility into the Base chain sequencer's pending transaction queue specifically for MEV, sandwich attack detection, or frontrunning signal extraction. Unlike Ethereum mainnet mempool scanners, this reflects Base's centralized sequencer queue rather than a p2p mempool.

## Known failure modes

- Payment not provided — returns 402 with x402 and MPP payment instructions
- Sequencer queue temporarily unavailable — may return 503 or empty results
- No large pending transactions currently in queue — returns empty list
- Rate limiting if demo quota exceeded without payment

## How this service works

Base sequencer pending transaction feed — large pending swaps, MEV opportunities, frontrunning signals. Base uses a centralized sequencer so this shows the sequencer queue rather than a traditional mempool.

## Output

A feed of pending transactions from the Base sequencer queue, highlighting large swaps, identified MEV opportunities, and frontrunning signals with relevant transaction metadata

## Example request

```json
{
 "chain": "base",
 "limit": 10,
 "filter": "large_swaps"
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "description": "Base sequencer pending transaction feed — large pending swaps, MEV opportunities, frontrunning signals. Base uses a centralized sequencer so this shows the sequencer queue rather than a traditional mempool."
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/httpay-xyz-d2bdc836/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from httpay.xyz](https://www.zero.xyz/host/httpay.xyz/llms.txt)