# Bitcoin Block Anomaly Detector

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

Detects and returns on-chain anomaly signals for a given Bitcoin block height, including fee-exceeds-subsidy, empty block, difficulty retarget, timestamp inversion, long block gap, and coinbase message anomalies.

## Facts

- Endpoint: GET https://obol-payai.fly.dev/signal/840000
- 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-block-anomaly-detector-ba80f1ec
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_jej875QBn043fxYE-ne0G

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-block-anomaly-detector-ba80f1ec
```

Example prompt: Check Bitcoin block 840000 for any on-chain anomalies — I want to know if it had unusually high fees, was empty, hit a difficulty retarget, had a timestamp inversion, a long gap, or anything weird in the coinbase message.

## When to prefer this

Use this endpoint when you need a lightweight, pre-validated, cryptographically verifiable anomaly signal for a specific Bitcoin block height without running your own node or writing custom detection logic. Ideal for agents that need trustworthy on-chain anomaly flags at low cost ($0.01 USDC per call) with independent verifiability.

## Known failure modes

- Invalid or non-integer block height returns a validation error
- Block height not yet mined returns a not-found or out-of-range error
- Payment not provided or insufficient returns HTTP 402 Payment Required
- Network or upstream Bitcoin node unavailability causes 503 or timeout
- Signature verification failure may indicate tampered response

## How this service works

Validation-gated Bitcoin block anomaly detector / on-chain anomaly signal for a block height: fee-exceeds-subsidy, empty block, difficulty retarget, timestamp inversion, long block gap, coinbase message. Only truth-tested detectors are served. Free height list: GET /examples. Cryptographically signed (Ed25519) — every response is independently verifiable via /.well-known/obol-pubkey.

## Output

Returns a cryptographically signed (Ed25519) anomaly signal object for the specified block height, indicating which anomaly detectors fired (fee-exceeds-subsidy, empty block, difficulty retarget, timestamp inversion, long block gap, coinbase message), along with verifiable proof via the public key at /.well-known/obol-pubkey.

## 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"
    },
    "pathParams": {
     "type": "object",
     "required": [
      "height"
     ],
     "properties": {
      "height": {
       "type": "integer"
      }
     }
    },
    "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-block-anomaly-detector-ba80f1ec/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from obol-payai.fly.dev](https://www.zero.xyz/host/obol-payai.fly.dev/llms.txt)