Data Fetch Skill: CoinGecko API with curl

Overview

This skill covers fetching live cryptocurrency market data using the CoinGecko public API and the curl command-line tool.

API Endpoint

Base URL: https://api.coingecko.com/api/v3

Market Data Endpoint:

code

GET /coins/markets

Required Parameters

Parameter	Value	Description
`vs_currency`	`usd`	Quote currency for prices
`order`	`market_cap_desc`	Sort by market cap descending
`per_page`	`50`	Number of coins to fetch
`sparkline`	`false`	Disable sparkline data (smaller response)

curl Command

Basic Fetch

bash

curl -s "https://api.coingecko.com/api/v3/coins/markets?vs_currency=usd&order=market_cap_desc&per_page=50&sparkline=false" -o crypto_raw.json

With Headers (recommended for reliability)

bash

curl -s \
  -H "Accept: application/json" \
  -H "User-Agent: CryptoWatchtower/1.0" \
  "https://api.coingecko.com/api/v3/coins/markets?vs_currency=usd&order=market_cap_desc&per_page=50&sparkline=false" \
  -o crypto_raw.json

curl Flags Explained

Flag	Purpose
`-s`	Silent mode (no progress bar)
`-o <file>`	Write output to file
`-H`	Add HTTP header
`-w "%{http_code}"`	Print HTTP status code
`--retry 3`	Retry failed requests

Response Structure

Each coin object contains:

json

{
  "id": "bitcoin",
  "symbol": "btc",
  "name": "Bitcoin",
  "current_price": 45000.00,
  "market_cap": 850000000000,
  "price_change_percentage_24h": 2.5,
  "total_volume": 25000000000,
  "high_24h": 46000.00,
  "low_24h": 44000.00
}

Error Handling

Rate Limiting

CoinGecko limits requests. If rate limited (HTTP 429):

bash

# Check status and retry
STATUS=$(curl -s -w "%{http_code}" -o crypto_raw.json "https://api.coingecko.com/api/v3/coins/markets?vs_currency=usd&order=market_cap_desc&per_page=50")
if [ "$STATUS" = "429" ]; then
  echo "Rate limited. Waiting 60 seconds..."
  sleep 60
  curl -s "https://api.coingecko.com/api/v3/coins/markets?vs_currency=usd&order=market_cap_desc&per_page=50" -o crypto_raw.json
fi

Validate Response

bash

# Check if valid JSON array
jq 'type' crypto_raw.json  # Should output: "array"
jq 'length' crypto_raw.json  # Should output: 50

Common Issues

•Empty response: Check internet connection
•Rate limited (429): Wait 60 seconds, or use API key
•Invalid JSON: API might be down, check status page
•Timeout: Add --max-time 30 flag