# fastapi.online — BTC Mempool Lookup

> fastapi.online — BTC Mempool Lookup is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.0005/call, status unknown (last checked 2026-10-16).

Queries the Bitcoin mempool for pending transaction data and network state via a self-hosted utility endpoint.

## Facts

- Endpoint: POST https://api.fastapi.online/btc-mempool?utm_source=zero.xyz
- Price: $0.0005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-btc-mempool-lookup-1a8af5cd
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_L15PSZ83-E-5m2y6rdIuD

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 fastapi-online-btc-mempool-lookup-1a8af5cd -d '<json body>'
```

Example prompt: Can you check the current Bitcoin mempool status for me — how congested is it right now and what are the pending transaction counts?

## When to prefer this

Choose this endpoint when you need a quick, pay-per-call, no-signup lookup of Bitcoin mempool state — especially useful for agents that occasionally need BTC network data without maintaining a full node or a subscription to a blockchain data provider.

## Known failure modes

- Empty or malformed POST body may return 400 or 422 validation error
- Upstream Bitcoin node unavailable may return 503 or timeout
- Payment not included or invalid x402 payment header returns 402 Payment Required
- Rate limiting or node sync issues may return stale or partial data

## How this service works

Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&amp;A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding &amp; crypto utilities, date/time calculators, geo/coordinate math, math &amp; finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.

## Output

Returns current Bitcoin mempool data including pending/unconfirmed transaction counts, mempool size, and potentially fee rate estimates or network congestion indicators.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [],
     "properties": {}
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastapi-online-btc-mempool-lookup-1a8af5cd/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.fastapi.online](https://www.zero.xyz/host/api.fastapi.online/llms.txt)