# Bitcoin Difficulty Retarget Anomaly Detector (Latest Block)

> Bitcoin Difficulty Retarget Anomaly Detector (Latest Block) is a paid API for AI agents from obol-x402.fly.dev, paid per call via x402, $0.01/call, status down (last checked 2026-09-15).

Checks the current Bitcoin chain tip for difficulty retarget anomalies and returns a cryptographically signed detection result

## Facts

- Endpoint: GET https://obol-x402.fly.dev/v1/btc/anomaly/difficulty-retarget/latest
- Price: $0.01/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/bitcoin-difficulty-retarget-anomaly-detector-latest-block-048d32d2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_LrXg_whikVDyr2OeHcD7W

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-difficulty-retarget-anomaly-detector-latest-block-048d32d2
```

Example prompt: Check the current Bitcoin chain tip right now and tell me if there's anything anomalous about the latest difficulty retarget — flag it if something looks off.

## When to prefer this

Use this endpoint when you need a fast, cryptographically verifiable check for Bitcoin difficulty retarget anomalies at the latest chain tip, especially in forensic pipelines, monitoring agents, or alerting systems that require tamper-evident signed responses. Prefer over manual node queries when you need a single signed attestation without running your own Bitcoin node.

## Known failure modes

- Payment not received or invalid — 402 response blocking access
- Bitcoin node unreachable or chain tip stale — data unavailable error
- No recent retarget epoch available — returns no anomaly or null result
- Signature verification failure if public key mismatch occurs
- Rate limit or service overload on the fly.dev host

## How this service works

Bitcoin difficulty retarget anomaly check on chain tip. Validation-gated detector difficulty_retarget for forensic and monitoring agents. Cryptographically signed (Ed25519) — every response is independently verifiable via /.well-known/obol-pubkey.

## Output

A signed JSON response indicating whether a difficulty retarget anomaly was detected at the current Bitcoin chain tip, including detection metadata and an Ed25519 signature verifiable via the service's public key endpoint.

## 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": {}
    }
   },
   "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-difficulty-retarget-anomaly-detector-latest-block-048d32d2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from obol-x402.fly.dev](https://www.zero.xyz/host/obol-x402.fly.dev/llms.txt)