# Crypto ETF Sentinel — Fee War History

> Crypto ETF Sentinel — Fee War History is a paid API for AI agents from api.cryptoetfsentinel.com, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-15).

Returns quarterly average and median expense ratios over time across the US spot crypto ETF cohort, documenting fee compression since the January 2024 spot Bitcoin ETF launch.

## Facts

- Endpoint: GET https://api.cryptoetfsentinel.com/v1/xbrl/fee-war/history
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/api-cryptoetfsentinel-com-340fbcb2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_dtubY5Yg80J-2Uj_AALY1

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 api-cryptoetfsentinel-com-340fbcb2
```

Example prompt: Show me how average and median expense ratios have changed quarter by quarter across all US spot crypto ETFs since the January 2024 Bitcoin ETF launch — I want to see the full fee-war compression history from Crypto ETF Sentinel.

## When to prefer this

Use this endpoint when you need a longitudinal, cohort-wide view of crypto ETF fee compression trends over time — specifically average and median expense ratios per quarter. Prefer this over single-issuer XBRL snapshots when your goal is market-level analysis of fee competition dynamics rather than one fund's current metrics.

## Known failure modes

- No data available if called before any quarterly data is recorded
- 402 Payment Required if x402 USDC payment of $0.10 is not submitted
- 503 Service Unavailable if upstream XBRL/SEC data pipeline is down
- Empty result set if cohort has no XBRL expense ratio filings yet

## How this service works

Crypto ETF Sentinel — Quarterly fee-war progression: average and median expense ratios over time across the US spot crypto ETF trading cohort, with per-issuer detail each quarter. Use when documenting how fee competition has compressed since the January 2024 spot Bitcoin ETF launch. Optional crypto filter.

## Output

A time-series dataset showing quarterly average and median expense ratios across the entire US spot crypto ETF trading cohort, illustrating how fee competition has evolved and compressed since spot Bitcoin ETFs launched in January 2024.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "properties": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/api-cryptoetfsentinel-com-340fbcb2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.cryptoetfsentinel.com](https://www.zero.xyz/host/api.cryptoetfsentinel.com/llms.txt)