# FastPath API - Bitcoin Fee Ladder

> FastPath API - Bitcoin Fee Ladder 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 tiered fee ladder (cheap/normal/urgent) with sat/vbyte estimates and block targets from Core v31 optimizer cache

## Facts

- Endpoint: POST https://api.nativebtc.org/v1/template/fee-ladder
- 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-fee-ladder-155726b4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8wsiOtUDpeHuax7v5CUvK

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-fee-ladder-155726b4 -d '<json body>'
```

Example prompt: What are the current Bitcoin fee tiers — cheap, normal, and urgent — in sat/vbyte from the Core v31 optimizer cache, targeting 6 blocks for normal confirmation?

## When to prefer this

Use this endpoint when you need a structured multi-tier Bitcoin fee recommendation (cheap/normal/urgent) derived from Bitcoin Core v31's optimizer cache, especially when building wallets, transaction fee selectors, or dashboards that need tiered fee guidance rather than a single point estimate.

## Known failure modes

- Invalid targetBlocks value (below minimum of 1) returns validation error
- Core v31 optimizer cache unavailable returns error or stale data
- Payment failure via x402 returns 402 Payment Required
- Network timeout returns 5xx server error

## 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 a fee ladder with three tiers: cheap (sat/vbyte and block target), normal (sat/vbyte and block target), and urgent (sat/vbyte and block target), along with the data source label and a success flag.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "targetBlocks": {
   "type": "number",
   "minimum": 1,
   "description": "Desired confirmation target in blocks."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ladder": {
   "cheap": {
    "satVb": 1,
    "targetBlocks": 144
   },
   "normal": {
    "satVb": 1,
    "targetBlocks": 6
   },
   "urgent": {
    "satVb": 2,
    "targetBlocks": 1
   }
  },
  "source": "core_v31_optimizer_cache",
  "success": true
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastpath-api-bitcoin-fee-ladder-155726b4/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)