# Carbon & Cashmere Beta-to-BTC Signal API – ETH

> Carbon & Cashmere Beta-to-BTC Signal API – ETH is a paid API for AI agents from api.carbon-cashmere.de, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Returns the beta coefficient of ETH relative to BTC, including market regime, stability classification, rolling 30-day statistics, R-squared fit, and daily alpha percentage.

## Facts

- Endpoint: GET https://api.carbon-cashmere.de/v1/beta-to-btc/ETH
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/carbon-cashmere-beta-to-btc-signal-api-eth-89479f3c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_GaPuDRiB_AghADvGigQQf

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 carbon-cashmere-beta-to-btc-signal-api-eth-89479f3c
```

Example prompt: What's ETH's current beta to BTC — is it in an amplifier regime, how stable is it, and what's the daily alpha looking like over the last 90 days?

## When to prefer this

Use this endpoint when you need quantitative beta and regime analytics for ETH relative to BTC — specifically when you want rolling statistics, market regime classification (amplifier/dampener), stability labels, and daily alpha. Prefer this over generic price endpoints when the use case is systematic risk measurement, portfolio hedging analysis, or momentum/mean-reversion regime detection for ETH specifically.

## Known failure modes

- Invalid or unsupported coin symbol returns an error
- Service unavailable if upstream market data feed is down
- Payment failure if USDC balance is insufficient for the $0.01 per-call fee
- Stale data if market data pipeline is delayed
- Malformed request returns 400-level error

## How this service works

Professional crypto market intelligence. Real-time prices, signals, and market scoring.

## Output

A JSON object containing ETH's beta coefficient relative to BTC (e.g. 1.12), the market regime label (e.g. 'amplifier'), stability classification (e.g. 'stable'), R-squared goodness-of-fit, rolling 30-day statistics (mean, std dev, current beta), the lookback period in days, and the daily alpha percentage.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "beta": 1.12,
  "coin": "ETH",
  "_meta": {
   "disclaimer": "Informational research data only — not investment advice."
  },
  "regime": "amplifier",
  "r_squared": 0.78,
  "stability": "stable",
  "rolling_30d": {
   "std": 0.08,
   "mean": 1.11,
   "current_beta": 1.15
  },
  "lookback_days": 90,
  "alpha_daily_pct": -0.02
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/carbon-cashmere-beta-to-btc-signal-api-eth-89479f3c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.carbon-cashmere.de](https://www.zero.xyz/host/api.carbon-cashmere.de/llms.txt)