# BTC Address Validator

> BTC Address Validator is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Validates whether a given string is a valid Bitcoin address

## Facts

- Endpoint: POST https://api.fastapi.online/btc-address
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/btc-address-validator-de6f9ddf
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_VkIYMbGNOrKkA1IbPBy3Y

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 btc-address-validator-de6f9ddf -d '<json body>'
```

Example prompt: Can you check if this is a valid Bitcoin address before I send funds to it: 1A1zP1eP5QGefi2DMPTfTL5SLmv7Divf NA?

## When to prefer this

Use this endpoint when you need a lightweight, pay-per-call Bitcoin address format and checksum validator with no API key or signup required. Prefer it for one-off or low-volume validation in automated payment workflows, especially when crypto micropayment (x402) billing is already in use and you want to avoid subscription overhead.

## Known failure modes

- Empty or missing address field returns validation error
- Non-BTC address strings (e.g. Ethereum addresses) may return invalid
- Malformed JSON body returns 422 Unprocessable Entity
- Network or server errors return 5xx with no result
- Payment not included or insufficient results in 402 Payment Required

## 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 whether the provided Bitcoin address is valid, and likely includes the address type (e.g. P2PKH, P2SH, Bech32) and any format or checksum details that confirm or deny its legitimacy.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "address": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/btc-address-validator-de6f9ddf/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)