# FastX402 Lab BTC Fees

> FastX402 Lab BTC Fees is a paid API for AI agents from lab.fastx402.tools, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-17).

Returns current Bitcoin mempool fee rates and mempool statistics for a given network (mainnet, testnet3, or testnet4)

## Facts

- Endpoint: GET https://lab.fastx402.tools/btc-fees?utm_source=zero.xyz
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-17
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastx402-lab-btc-fees-18d14f11
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Zph8U7gjR82KK2HWxFww-

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 fastx402-lab-btc-fees-18d14f11
```

Example prompt: What are the current Bitcoin fee rates on mainnet — I need economy, 30-minute, 1-hour, and fastest sat/vb estimates, plus how congested the mempool is right now?

## When to prefer this

Choose this endpoint when an AI agent needs real-time Bitcoin fee estimates to set transaction fees or assess mempool congestion, especially in a pay-per-call context where no API key or signup is desired. It is well-suited for lightweight, infrequent fee lookups paid in USDC on Base via x402.

## Known failure modes

- Invalid network value returns an error (valid values: main, testnet3, testnet4)
- Network or upstream mempool data unavailable returns a server error
- Payment failure or insufficient USDC balance prevents call from completing

## How this service works

FastX402 Lab: small pay-per-call tools for AI agents, paid per request in USDC on Base over x402. No signup, no API key.

## Output

A JSON object containing the queried network name, fee rates in sat/vbyte for four confirmation targets (economy, one_hour, thirty_minutes, fastest), and mempool statistics including total virtual size in bytes, transaction count, and total fees in satoshis.

## 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",
     "required": [],
     "properties": {
      "network": {
       "type": "string",
       "description": "Bitcoin network to query: main, testnet3 or testnet4. Defaults to main."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "mempool": {
       "type": "object",
       "properties": {
        "vsize": {
         "type": "integer"
        },
        "transactions": {
         "type": "integer"
        },
        "total_fee_sat": {
         "type": "integer"
        }
       }
      },
      "network": {
       "type": "string"
      },
      "fee_rates_sat_vb": {
       "type": "object",
       "properties": {
        "economy": {
         "type": "integer"
        },
        "fastest": {
         "type": "integer"
        },
        "one_hour": {
         "type": "integer"
        },
        "thirty_minutes": {
         "type": "integer"
        }
       }
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "mempool": {
   "vsize": 30000000,
   "transactions": 5000,
   "total_fee_sat": 61234567
  },
  "network": "main",
  "fee_rates_sat_vb": {
   "economy": 10,
   "fastest": 20,
   "one_hour": 15,
   "thirty_minutes": 17
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastx402-lab-btc-fees-18d14f11/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from lab.fastx402.tools](https://www.zero.xyz/host/lab.fastx402.tools/llms.txt)