Adding External Data — Crypto Fear & Greed Index

The Open Interest tutorial walked through the mechanics of the External Indicator dialog using a Binance endpoint. This is the same flow but for a different kind of provider — the alternative.me Fear & Greed Index, a widely-cited daily sentiment score for the crypto market.

The point of doing it twice with different providers: the dialog doesn't care whether the data comes from an exchange, a market-data API, or some random JSON endpoint someone runs in a Hetzner box. As long as the response is JSON and the values you want are reachable via JSONPath, you can wire it in.

What the index measures

The Crypto Fear & Greed Index is a single 0–100 number, updated daily, blending five inputs:

• Volatility (25%)
• Market momentum / volume (25%)
• Social media sentiment (15%)
• Survey data (15%) — currently paused
• Bitcoin dominance (10%)
• Google Trends data (10%)

Interpretation:

Range	Label	Reading
0–24	Extreme Fear	Capitulation, often a buying opportunity
25–49	Fear	Risk-off mood
50	Neutral
51–74	Greed	Risk-on, getting frothy
75–100	Extreme Greed	Often precedes corrections

Strategies use it as a contrarian regime filter — only buy when the market is fearful, only short when it's greedy — or as a sizing input where larger positions go on during extreme readings in the direction you're trading against.

The API

alternative.me's endpoint is unauthenticated and dead simple:

https://api.alternative.me/fng/?limit=N

Sample response:

{
  "name": "Fear and Greed Index",
  "data": [
    {"value": "47", "value_classification": "Neutral", "timestamp": "1777248000"},
    {"value": "33", "value_classification": "Fear", "timestamp": "1777161600"}
  ],
  "metadata": {"error": null}
}

Notes:

• value is a string containing a number 0–100. The platform's JSONPath extraction parses it via float() so this works fine.
• timestamp is Unix seconds as a string. Set the response timestamp format to Unix (seconds or milliseconds) and the platform handles it.
• value_classification is the human-readable label. External Indicators are numeric only, so we use value. If you need the label, classify in your strategy's logic (e.g., if value < 25 then extreme_fear).
• The endpoint takes only limit, not startTime / endTime. We ignore the date placeholders entirely and let the platform fetch the most recent N values, then align them by timestamp.

Configure the indicator

Click + External Indicator in the right panel. (See the OI tutorial for what the dialog looks like.)

Fill in:

Field	Value
Indicator Name	Crypto Fear & Greed Index
Historical Data URL	https://api.alternative.me/fng/?limit={limit}
Auth Header / API Key	(blank — public endpoint)
Output → name	value
Output → value JSONPath	$.data[*].value
Output → timestamp JSONPath	$.data[*].timestamp
Response Timestamp Format	Unix (seconds or milliseconds)
URL Param Date Format	(any — this API doesn't take date params; the placeholders are ignored)
Mode	Latest from historical
Latest-from-Historical URL	https://api.alternative.me/fng/?limit=1
Refresh Interval (seconds)	3600

Why 3600? The index updates once per day. Polling every hour is generous; you could easily go to 21600 (6 hours) without losing anything practical.

The JSONPath syntax $.data[*].value walks into the data object's array and grabs the value field of each entry — different from the OI example's $[*].sumOpenInterest, which started directly at a root-level array. JSONPath naturally handles both shapes.

Test and save

Click Test Connection — successful output looks like this:

Success! Found 7 data points across 1 output(s) — value: 7 points

Click Save Indicator. You'll now have two External Indicators side by side in the right panel — one from a futures exchange, one from a sentiment aggregator — both behaving identically:

Using it

The indicator is now in the Blockly Indicators category as Crypto Fear & Greed Index Output value. You can compare it against thresholds (< 25 = extreme fear), drop it into compound conditions, or reference it from a Signal definition.

A simple regime use: only enter long positions when Crypto Fear & Greed Index Output value < 30 AND your normal trigger fires. The fear-and-greed score becomes a contrarian gate on the rest of the strategy.

What's different from the OI example?

Almost nothing — and that's the point. Same dialog, same flow, same blocks in your strategy. The differences are:

• Different URL — pointing at alternative.me instead of Binance
• Different JSONPath — the response is {data: [...]} instead of a root-level array
• Different cadence — daily updates instead of 5-minute updates, so a longer refresh interval makes sense
• No date placeholders work — alternative.me only takes limit, so we let the platform fetch a fixed window of recent points

For any other JSON-returning API the work is the same: figure out the URL pattern, write the JSONPath to extract the value and timestamp, pick a sensible refresh interval. Everything downstream — backtest support, live trading, strategy blocks — comes for free.