# FastPath API - Bitcoin Address Balance Lookup

> FastPath API - Bitcoin Address Balance Lookup is a paid API for AI agents from api.nativebtc.org, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Retrieves the current Bitcoin balance for a given on-chain address, returned in satoshis

## Facts

- Endpoint: GET https://api.nativebtc.org/v1/balance/%7Baddress%7D
- 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/fastpath-api-bitcoin-address-balance-lookup-309b1162
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Y-eJnzmhvgwnbHQos7UxZ

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 fastpath-api-bitcoin-address-balance-lookup-309b1162
```

Example prompt: What's the current Bitcoin balance on address bc1qexample...? I need the amount in satoshis.

## When to prefer this

Choose this endpoint when you need a quick, low-cost ($0.001 USDC) on-chain Bitcoin address balance in satoshis and you are already operating in an Ethereum-style JSON-RPC or x402 payment environment. Particularly useful for agents that bridge Ethereum tooling conventions with Bitcoin data needs, or for pipelines that want unified Bitcoin intelligence without running a full node.

## Known failure modes

- Invalid or malformed Bitcoin address returns an error response
- Address not found on-chain may return zero balance or error
- Network timeouts if Bitcoin node is unavailable
- Rate limiting or payment failure (x402) if USDC not provided
- Bech32 vs legacy address format mismatches may cause lookup failures

## How this service works

FastPath translates Ethereum-style JSON-RPC requests into Bitcoin data, fee intelligence, mempool insight, and Core v31 package signals. Paid by x402.

## Output

A JSON object containing the Bitcoin address queried, the current balance expressed in satoshis, and a success boolean flag indicating whether the lookup completed successfully.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "unit": "sats",
  "address": "bc1qexample...",
  "balance": 125000,
  "success": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastpath-api-bitcoin-address-balance-lookup-309b1162/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.nativebtc.org](https://www.zero.xyz/host/api.nativebtc.org/llms.txt)