# Bitcoin Fee Exceeds Subsidy Anomaly Detector

> Bitcoin Fee Exceeds Subsidy Anomaly Detector 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 whether Bitcoin transaction fees on the current chain tip exceed the block subsidy, flagging this rare anomaly with a cryptographically signed Ed25519 response.

## Facts

- Endpoint: GET https://obol-x402.fly.dev/v1/btc/anomaly/fee-exceeds-subsidy/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-fee-exceeds-subsidy-anomaly-detector-dbe45cb6
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_EQ8EzaCE9puhYHwI7pLzF

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-fee-exceeds-subsidy-anomaly-detector-dbe45cb6
```

Example prompt: Check the latest Bitcoin block and tell me if total transaction fees exceeded the block subsidy — flag it as an anomaly if so, and give me the signed result.

## When to prefer this

Use this endpoint when you need a lightweight, pay-per-call, cryptographically verifiable check on whether Bitcoin transaction fees have exceeded the block subsidy on the current chain tip — ideal for forensic agents, monitoring pipelines, and anomaly alert systems that require tamper-evident responses. Prefer this over general block explorers when you need structured anomaly detection with Ed25519-signed output rather than raw block data.

## Known failure modes

- Bitcoin node data unavailable — upstream connection to chain tip may be down
- Payment not processed — x402 payment of $0.01 USDC required before data is returned
- Invalid or expired chain tip data — block data may be momentarily stale during reorg
- Signature verification failure — Ed25519 signature mismatch indicating tampered response

## How this service works

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

## Output

Returns a signed (Ed25519) JSON response indicating whether fees on the current Bitcoin chain tip exceed the block subsidy, including the anomaly flag (fee_exceeds_subsidy), relevant block metadata, and a cryptographic signature verifiable 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"
    },
    "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-fee-exceeds-subsidy-anomaly-detector-dbe45cb6/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)