# FastPath API – Bitcoin Data via Ethereum JSON-RPC

> FastPath API – Bitcoin Data via Ethereum JSON-RPC is a paid API for AI agents from api.nativebtc.org, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Translates Ethereum-style JSON-RPC requests into Bitcoin blockchain data, fee estimates, mempool insights, and Bitcoin Core v31 package signals.

## Facts

- Endpoint: POST https://api.nativebtc.org/v1/rpc
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastpath-api-bitcoin-data-via-ethereum-json-rpc-0d53e79f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_m3Z9ACN50NR4dq5kz_1DA

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-data-via-ethereum-json-rpc-0d53e79f -d '<json body>'
```

Example prompt: What are the current Bitcoin fee tiers — cheap, normal, and urgent in sat/vB — using the fastpath_feeLadder method so I know how fast each target confirmation time is?

## When to prefer this

Choose this endpoint when you need Bitcoin fee intelligence or mempool data but your agent stack is already wired for Ethereum JSON-RPC — FastPath lets you reuse existing eth_ method plumbing to get Bitcoin data without building a separate Bitcoin RPC client. Particularly useful for developers familiar with eth_blockNumber and eth_getBalance patterns who want Bitcoin Core v31 fee signals without learning a new protocol.

## Known failure modes

- Invalid method name returns JSON-RPC error with code -32601 (method not found)
- Malformed params array returns -32602 (invalid params)
- Payment failure or insufficient USDC balance returns HTTP 402 before processing
- Bitcoin Core backend unavailable returns -32603 (internal error)
- Unsupported Ethereum method with no Bitcoin equivalent returns error response

## 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-RPC 2.0 response object containing fee ladder tiers (cheap, normal, urgent) each with sat/vB rate and target confirmation blocks, sourced from Bitcoin Core v31 optimizer cache, plus any additional Bitcoin data (block height, mempool state, transaction info) depending on the method called.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "id": {
   "description": "Client-selected JSON-RPC request id."
  },
  "method": {
   "type": "string",
   "description": "Ethereum-style method or FastPath method, for example eth_blockNumber, eth_getBalance, fastpath_feeLadder, or fastpath_bitcoinInsight."
  },
  "params": {
   "type": "array",
   "description": "JSON-RPC params for the selected method."
  },
  "jsonrpc": {
   "type": "string",
   "const": "2.0"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": 1,
  "result": {
   "cheap": {
    "satVb": 1,
    "targetBlocks": 144
   },
   "normal": {
    "satVb": 1,
    "targetBlocks": 6
   },
   "source": "core_v31_optimizer_cache",
   "urgent": {
    "satVb": 2,
    "targetBlocks": 1
   }
  },
  "jsonrpc": "2.0"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastpath-api-bitcoin-data-via-ethereum-json-rpc-0d53e79f/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)