# FastPath API - Bitcoin RBF Bump Plan

> FastPath API - Bitcoin RBF Bump Plan is a paid API for AI agents from api.nativebtc.org, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Returns a Replace-By-Fee (RBF) bump plan for an unconfirmed Bitcoin transaction, including current and target fee amounts needed to reach a desired confirmation block target.

## Facts

- Endpoint: POST https://api.nativebtc.org/v1/template/bump-plan
- Price: $0.01/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-rbf-bump-plan-056455be
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zqi6ckmOuPBWkRsD3Hv9l

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-rbf-bump-plan-056455be -d '<json body>'
```

Example prompt: My Bitcoin transaction with txid a3f1b2c4d5e6f7890123456789abcdef0123456789abcdef0123456789abcdef01 has been stuck for hours — can you give me a fee bump plan to get it confirmed within 3 blocks using RBF?

## When to prefer this

Use this endpoint when you need to programmatically calculate how much additional fee is required to bump an unconfirmed Bitcoin transaction to a specific block confirmation target via Replace-By-Fee. Prefer this over generic fee estimators when you have a specific txid and need a tailored bump plan rather than a general fee rate. Ideal for wallets, payment processors, or agents managing time-sensitive Bitcoin transactions.

## Known failure modes

- Invalid txid format (not 64 hex characters) returns a validation error
- Transaction not found in mempool or already confirmed may return available: false
- targetBlocks below minimum (1) returns a schema validation error
- Transaction not signaling RBF may return available: false
- Network congestion or node connectivity issues may cause delays or 5xx errors

## 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

Returns a JSON object indicating the RBF bump method (e.g. rbf_signed_replacement), whether a bump is available, the current fee in satoshis, the target fee in satoshis for the desired block confirmation, the additional satoshis required, and whether the service signs or custodies funds (always false).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "txid": {
   "type": "string",
   "pattern": "^[0-9a-fA-F]{64}$",
   "description": "Bitcoin transaction ID as 64 lowercase or uppercase hex characters."
  },
  "targetBlocks": {
   "type": "number",
   "minimum": 1,
   "description": "Desired confirmation target in blocks."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "method": "rbf_signed_replacement",
  "success": true,
  "available": true,
  "targetFeeSats": 330,
  "currentFeeSats": 220,
  "additionalFeeSats": 110,
  "signsOrCustodiesFunds": false
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastpath-api-bitcoin-rbf-bump-plan-056455be/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)