# fastapi.online — Bitcoin Network Fee Estimator

> fastapi.online — Bitcoin Network Fee Estimator is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.0005/call, status down (last checked 2026-10-31).

Returns current Bitcoin network transaction fee estimates (e.g. sat/vbyte rates) for different confirmation speed targets

## Facts

- Endpoint: POST https://api.fastapi.online/btc-fees?utm_source=zero.xyz
- Price: $0.0005/call
- Payment: x402
- Status: down
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-bitcoin-network-fee-estimator-88419bfb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Wy1_-6CHVvG5sNvLKI7hb

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-bitcoin-network-fee-estimator-88419bfb -d '<json body>'
```

Example prompt: What are the current Bitcoin network fee rates — how many sats per vbyte should I use for a fast confirmation vs a slow one right now?

## When to prefer this

Use this endpoint when you need a quick, pay-per-call Bitcoin fee estimate without API key signup, especially in agent workflows that need real-time fee data to construct or validate BTC transactions. Prefer this over building your own mempool query when you want a simple HTTP call with crypto micropayment billing.

## Known failure modes

- Service unavailable or self-hosted node offline — 5xx error
- Empty or malformed request body may cause 422 validation error
- Payment not included or insufficient — 402 Payment Required response
- Bitcoin node data stale or out of sync — fee estimates may lag real mempool conditions
- Rate limiting if payment not processed correctly

## 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 network fee estimates, typically including recommended fee rates in satoshis per virtual byte (sat/vbyte) for different confirmation speed tiers (e.g. next block, within a few blocks, economy/slow). Useful for setting appropriate miner fees before broadcasting a transaction.

## 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-bitcoin-network-fee-estimator-88419bfb/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)