# Bitcoin Transaction Fee Rates & Mempool Congestion

> Bitcoin Transaction Fee Rates & Mempool Congestion is a paid API for AI agents from api.agentstools.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Returns recommended Bitcoin transaction fee rates in sat/vByte across five confirmation speed tiers plus a live mempool congestion snapshot with estimated block backlog.

## Facts

- Endpoint: GET https://api.agentstools.dev/btc/fees
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/bitcoin-transaction-fee-rates-mempool-congestion-7b52950e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_G_lzz8V5VGRYS3yeTddx2

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 bitcoin-transaction-fee-rates-mempool-congestion-7b52950e
```

Example prompt: What are the current Bitcoin fee rates — fastest, economy, and minimum — and is the mempool congested right now? I want to know how many blocks are backlogged.

## When to prefer this

Choose this endpoint when an agent needs current Bitcoin fee recommendations across multiple confirmation horizons in a single call, especially when building transaction fee UIs, wallets, or automated Bitcoin transaction submission workflows. Prefer over generic blockchain explorers when you specifically need multi-tier fee estimates plus mempool congestion context in one response.

## Known failure modes

- Upstream Bitcoin node or mempool data source is unavailable — returns 5xx error
- Payment not received or invalid x402 payment header — returns 402 Payment Required
- Rate limit exceeded — returns 429 Too Many Requests
- Mempool data may be slightly stale if the underlying data source lags

## How this service works

Recommended Bitcoin transaction fee-rates in sat per vByte across five confirmation horizons (fastest, half hour, hour, economy, minimum) plus a live mempool congestion snapshot with an estimated block backlog. Informational, not advice.

## Output

Returns five fee-rate tiers (fastest, half-hour, hour, economy, minimum) each expressed in satoshis per virtual byte, plus a live mempool congestion indicator and an estimated number of blocks currently backlogged waiting for confirmation.

## 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",
     "required": [],
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/bitcoin-transaction-fee-rates-mempool-congestion-7b52950e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.agentstools.dev](https://www.zero.xyz/host/api.agentstools.dev/llms.txt)