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 $0.002
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 /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 Payment Required 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"
}Bitcoin address balance and activity: check the balance and transactions of a Bitcoin address $0.01
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 /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 Payment Required 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
}Questions
Where do the numbers come from?
The mempool.space API, at call time.
How do I pay?
Each successful call costs the tool's price; failed calls are not charged. The first 25 calls are free. Then pay with card credits from $1 (the key goes in an Authorization header or as api_key= in the URL) or per call in USDC over x402 or MPP. No account is needed.