# FastPath Bitcoin Mempool Fee Estimator

> FastPath Bitcoin Mempool Fee Estimator 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).

Returns recommended Bitcoin fee rates (sat/vB) and fee histogram data for a specified confirmation target window

## Facts

- Endpoint: GET https://api.nativebtc.org/v1/mempool/fees
- 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-bitcoin-mempool-fee-estimator-d9338b64
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_QTXXqjsnYO7BXa3dSwYQQ

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-bitcoin-mempool-fee-estimator-d9338b64
```

Example prompt: What fee rate in sat/vB should I use to get my Bitcoin transaction confirmed within 10 blocks, and can you show me the mempool fee histogram?

## When to prefer this

Use this endpoint when you need to estimate Bitcoin transaction fees based on current mempool conditions, especially when you want both a specific recommended sat/vB rate and a histogram of fee distribution. Prefer this over generic fee APIs when you need Core v31-aligned fee intelligence with Ethereum-style JSON-RPC compatibility.

## Known failure modes

- Invalid target parameter (below minimum of 1 block) returns validation error
- Network unavailable or mempool data stale returns error response
- Payment not processed via x402 protocol results in 402 Payment Required
- Target confirmation window too large may return no data

## 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 with the recommended fee rate in satoshis per vByte for the requested confirmation target, a success flag, the target block count, and a histogram array showing transaction volume bucketed by fee range.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "target": {
       "type": "number",
       "minimum": 1,
       "description": "Target confirmation window in blocks."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "target": 10,
  "success": true,
  "histogram": [
   {
    "txs": 12000,
    "bucket": "1-2"
   }
  ],
  "recommendedSatVb": 1
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastpath-bitcoin-mempool-fee-estimator-d9338b64/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)