# Bitcoin fee estimate API

Current Bitcoin network fee rates in sat/vB for next-block, half-hour, one-hour and economy confirmation, the estimated cost in sats of a typical payment, mempool size and total pending fees, and the latest block height. Use before sending a Bitcoin transaction or to decide whether to wait for lower fees.

## When an agent wants this

- Pick a fee rate for the next block, half hour or hour
- Estimate the cost of a typical payment in sats
- Watch mempool congestion

## Bitcoin fee rates and mempool status: Bitcoin fee estimate in sat/vB for the next block, half hour and hour, with mempool size

Bitcoin fee rates and mempool status: Bitcoin fee estimate in sat/vB for the next block, half hour and hour, with mempool size. $0.002 per successful call; failed calls are never charged.

Current Bitcoin network fee rates in sat/vB for next-block, half-hour, one-hour and economy confirmation, the estimated cost in sats of a typical payment, mempool size and total pending fees, and the latest block height. Use before sending a Bitcoin transaction or to decide whether to wait for lower fees.

Inputs: .

Free first (25 successful calls per caller, no key):

    curl "https://tools.funwords.eu/btc-fees?format=json&trial=1"

With a card key from https://tools.funwords.eu/credits, in a header or, when your client can only fetch a URL, in the URL:

    curl -H "Authorization: Bearer adt_…" "https://tools.funwords.eu/btc-fees?format=json"
    curl "https://tools.funwords.eu/btc-fees?format=json&api_key=adt_…"

Without a key the same URL answers 402 with x402 and MPP terms, so a wallet client pays USDC per call and retries. Over MCP (https://tools.funwords.eu/mcp) this tool is btc_fees.

Example result:

    {
      "network": "bitcoin",
      "unit": "sat/vB",
      "fees": {
        "nextBlock": 4,
        "halfHour": 3,
        "hour": 1,
        "economy": 1,
        "minimum": 1
      },
      "typicalPaymentSats": {
        "nextBlock": 564,
        "hour": 141
      },
      "typicalPaymentVbytes": 141,
      "source": "https://mempool.space/api",
      "limitations": [
        "Estimates do not guarantee confirmation time",
        "141 vB is an illustrative one-input/two-output SegWit size; actual transaction size varies",
        "Source endpoints are fetched concurrently, not as an atomic snapshot"
      ],
      "mempool": {
        "transactions": 83832,
        "vsize": 42066150,
        "totalFeesBtc": 0.1093664
      },
      "blockHeight": 970000,
      "checkedAt": "2026-10-01T00:00:00.000Z"
    }

Tool page: https://tools.funwords.eu/tools/btc-fees

## Bitcoin address balance and activity: check the balance and transactions of a Bitcoin address

Bitcoin address balance and activity: check the balance and transactions of a Bitcoin address. $0.01 per successful call; failed calls are never charged.

Bitcoin address balance and activity for any mainnet address (legacy, P2SH or bech32): confirmed balance in sats and BTC, unconfirmed pending amount, total received and sent, and transaction counts. Use for payment verification, checking whether a deposit arrived, and wallet monitoring.

Inputs: address (required): Bitcoin mainnet address (1..., 3... or bc1...).

Free first (25 successful calls per caller, no key):

    curl "https://tools.funwords.eu/btc-address?address=bc1qxy2kgdygjrsqtzq2n0yrf2493p83kkfjhx0wlh&trial=1"

With a card key from https://tools.funwords.eu/credits, in a header or, when your client can only fetch a URL, in the URL:

    curl -H "Authorization: Bearer adt_…" "https://tools.funwords.eu/btc-address?address=bc1qxy2kgdygjrsqtzq2n0yrf2493p83kkfjhx0wlh"
    curl "https://tools.funwords.eu/btc-address?address=bc1qxy2kgdygjrsqtzq2n0yrf2493p83kkfjhx0wlh&api_key=adt_…"

Without a key the same URL answers 402 with x402 and MPP terms, so a wallet client pays USDC per call and retries. Over MCP (https://tools.funwords.eu/mcp) this tool is btc_address.

Example result:

    {
      "network": "bitcoin",
      "address": "bc1qxy2kgdygjrsqtzq2n0yrf2493p83kkfjhx0wlh",
      "balanceSats": 392247777,
      "balanceBtc": 3.92247777,
      "pendingSats": 0,
      "totalReceivedBtc": 16.79253616,
      "totalSentBtc": 12.87005839,
      "transactions": 1138,
      "pendingTransactions": 0
    }

Tool page: https://tools.funwords.eu/tools/btc-address

## Questions

Docs for agents: https://tools.funwords.eu/llms.txt · OpenAPI: https://tools.funwords.eu/openapi.json · All guides: https://tools.funwords.eu/guides