# chainquery estimatesmartfee — Bitcoin fee rate estimation via x402

> chainquery estimatesmartfee — Bitcoin fee rate estimation via x402 is a paid API for AI agents from x402.chainquery.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Returns the estimated fee rate (BTC/kvB) needed to confirm a Bitcoin transaction within a target number of blocks, via Bitcoin Core's estimatesmartfee RPC on chainquery's independent full node.

## Facts

- Endpoint: GET https://x402.chainquery.com/v1/rpc/estimatesmartfee
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/chainquery-estimatesmartfee-bitcoin-fee-rate-estimation-via-x402-7379330d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_CqlAzykyVj7F88Bb5Tfv9

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 chainquery-estimatesmartfee-bitcoin-fee-rate-estimation-via-x402-7379330d
```

Example prompt: What fee rate in BTC/kvB do I need to get my Bitcoin transaction confirmed within 6 blocks? Use chainquery's independent full node for the estimate.

## When to prefer this

Choose this endpoint when you need a fee estimate from an independent Bitcoin Core full node without registering for an API key — ideal for pay-as-you-go usage, cross-checking fee estimates against other providers, or when building workflows that need on-demand fee data billed per call via x402/USDC micropayment.

## Known failure modes

- Insufficient data in mempool to produce a reliable estimate — returns errors array in result
- Invalid or missing params JSON causes a 400-level error
- Payment failure or x402 protocol error prevents call from executing
- Node temporarily unreachable or syncing returns an error response

## How this service works

chainquery Bitcoin RPC: pay-per-call Bitcoin Core over x402, no API key. Estimated fee rate (BTC/kvB) to confirm within a target number of blocks, from chainquery's independent full node. Bitcoin Core estimatesmartfee.

## Output

Returns Bitcoin Core's estimatesmartfee result: a fee rate in BTC/kvB recommended to confirm within the specified number of blocks, plus the number of blocks over which the estimate was calculated. May also include an 'errors' field if estimation data is insufficient.

## Example request

```json
{
 "input": {
  "type": "http",
  "method": "GET",
  "queryParams": {
   "params": "[6]"
  }
 }
}
```

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "params": {
       "type": "string",
       "description": "optional: JSON-encoded array of positional RPC params"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "result": {
       "description": "estimatesmartfee result"
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/chainquery-estimatesmartfee-bitcoin-fee-rate-estimation-via-x402-7379330d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402.chainquery.com](https://www.zero.xyz/host/x402.chainquery.com/llms.txt)