CoinGecko API

Overview

Query cryptocurrency market data using the CoinGecko API V3. This skill covers:

• Price lookups by coin ID, symbol, or contract address
• Market data with rankings, volume, and price changes
• Historical price charts and OHLC data
• Search and trending coins
• Global market statistics

Scope: Covers the Demo (free), Analyst, Lite, and Pro tiers. For on-chain DEX data (GeckoTerminal endpoints), consult the fallback documentation.

Prerequisites

API Key Detection

Before making any API call, determine the available API key:

if [ -n "$COINGECKO_PRO_API_KEY" ]; then
  CG_BASE="https://pro-api.coingecko.com/api/v3"
  CG_AUTH=(-H "x-cg-pro-api-key: $COINGECKO_PRO_API_KEY")
elif [ -n "$COINGECKO_API_KEY" ]; then
  CG_BASE="https://api.coingecko.com/api/v3"
  CG_AUTH=(-H "x-cg-demo-api-key: $COINGECKO_API_KEY")
else
  CG_BASE="https://api.coingecko.com/api/v3"
  CG_AUTH=()
  echo "Warning: No CoinGecko API key found. Using keyless access (stricter rate limits)."
  echo "For higher limits, set COINGECKO_API_KEY or COINGECKO_PRO_API_KEY."
fi

API Tiers

Authentication via HTTP header (recommended). Query parameters (x_cg_demo_api_key / x_cg_pro_api_key) also work.

Coin ID Resolution

CoinGecko uses string IDs (e.g., bitcoin, ethereum, uniswap) rather than symbols. Before querying, resolve the correct coin ID.

Resolution Strategy

1. Common coins — Use well-known IDs directly: bitcoin, ethereum, solana, cardano, chainlink, uniswap, aave, maker. Note that some IDs diverge from the coin name: binancecoin (BNB), avalanche-2 (AVAX), polygon-ecosystem-token (POL) — see the table below.
2. Symbol lookup — Use /simple/price with the symbols parameter for quick lookups: symbols=btc,eth. Symbols are not unique — multiple coins can share the same symbol. By default, only the top-market-cap coin per symbol is returned; pass include_tokens=all to get all matches.
3. Ambiguous symbols — If a symbol maps to multiple coins (e.g., "UNI" could be Uniswap or Universe), use /search?query=<name> to disambiguate. Always verify the result matches the user's intent.
4. Contract address — Use /simple/token_price/{platform_id} when a contract address is provided.
5. Unknown coins — Use /search?query=<term> to find the correct ID before querying.

Common Coin IDs

Platform Resolution

Do not default to Ethereum. Always infer the platform from the user's prompt before making contract-based API calls.

Inference Rules

1. Explicit platform mention — If the user mentions a chain name (e.g., "on Polygon", "Arbitrum token", "Base chain"), map it to the corresponding platform ID (see ./references/platforms.md).
2. Platform-specific tokens — Some tokens exist primarily on specific platforms:
   • SOL, BONK, JUP → Solana (solana)
   • POL → Polygon (polygon-pos)
   • ARB → Arbitrum One (arbitrum-one)
   • OP → Optimism (optimistic-ethereum)
3. Address format hints — Base58 addresses (no 0x prefix) may be Solana or Tron — ask the user to clarify. 0x-prefixed addresses are EVM but exist on multiple chains.
4. Testnet keywords — Words like "testnet", "Sepolia", "Goerli", "devnet" indicate testnets. CoinGecko does not index testnet tokens — inform the user immediately.
5. Ambiguous cases — If the platform cannot be inferred, ask the user before proceeding. Do not assume Ethereum.

Unsupported Platforms

If the user references a chain not indexed by CoinGecko, respond with:

The chain "[chain name]" is not supported by the CoinGecko API.

For the current list of supported platforms, query:
https://api.coingecko.com/api/v3/asset_platforms

For a curated list of common platforms, see ./references/platforms.md. For the full live index, query the endpoint above.

Core Workflows

Quick Price Check

Fetch current price for one or more coins:

curl -s "$CG_BASE/simple/price?ids=bitcoin,ethereum&vs_currencies=usd&include_24hr_change=true&include_market_cap=true" "${CG_AUTH[@]}"

For symbol-based lookups:

curl -s "$CG_BASE/simple/price?symbols=btc,eth&vs_currencies=usd" "${CG_AUTH[@]}"

Token Price by Contract Address

Fetch price using a contract address on a specific chain:

curl -s "$CG_BASE/simple/token_price/ethereum?contract_addresses=0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48&vs_currencies=usd&include_market_cap=true" "${CG_AUTH[@]}"

Common platform IDs: ethereum, polygon-pos, arbitrum-one, optimistic-ethereum, base, avalanche, binance-smart-chain. For the full list, see ./references/platforms.md.

Token Logo

The /coins/{id} response includes logo URLs in the image object:

Fetch via /coins/{id} or /coins/{platform}/contract/{address} — the image field is present in both responses.

Market Rankings

Fetch top coins by market cap with detailed data:

curl -s "$CG_BASE/coins/markets?vs_currency=usd&order=market_cap_desc&per_page=10&page=1&price_change_percentage=24h,7d" "${CG_AUTH[@]}"

Historical Price Data

Fetch price history for charts:

# Last 7 days (hourly granularity)
curl -s "$CG_BASE/coins/bitcoin/market_chart?vs_currency=usd&days=7" "${CG_AUTH[@]}"

# Last 365 days (daily granularity)
curl -s "$CG_BASE/coins/bitcoin/market_chart?vs_currency=usd&days=365" "${CG_AUTH[@]}"

Auto-granularity: 1 day → 5-min intervals, 2-90 days → hourly, >90 days → daily.

Response contains prices, market_caps, and total_volumes arrays of [timestamp_ms, value] pairs.

OHLC / Candlestick Data

Fetch OHLC data for charting:

curl -s "$CG_BASE/coins/bitcoin/ohlc?vs_currency=usd&days=7" "${CG_AUTH[@]}"

Returns [[timestamp, open, high, low, close], ...]. Valid days values: 1, 7, 14, 30, 90, 180, 365, max.

Global Market Stats

curl -s "$CG_BASE/global" "${CG_AUTH[@]}"

Returns total market cap, 24h volume, BTC/ETH dominance percentages, and active cryptocurrencies count.

Search for a Coin

curl -s "$CG_BASE/search?query=sablier" "${CG_AUTH[@]}"

Returns matching coins, exchanges, categories, and NFTs sorted by market cap.

Trending Coins

curl -s "$CG_BASE/search/trending" "${CG_AUTH[@]}"

Returns top trending coins based on CoinGecko search activity.

Output Formatting

Default behavior: Present results in a Markdown table:

| Coin | Price (USD) | 24h Change | Market Cap |
| ---- | ----------- | ---------- | ---------- |
| Bitcoin | $67,187.34 | +3.64% | $1.32T |
| Ethereum | $3,456.78 | +2.15% | $415.2B |

User preference: If the user requests a specific format (JSON, CSV, plain text), use that format instead.

Number Formatting

• Prices > $1: 2 decimal places (e.g., $67,187.34)
• Prices $0.01–$1: 4 decimal places (e.g., $0.4523)
• Prices < $0.01: 6+ decimal places (e.g., $0.000001234)
• Market caps: abbreviated (e.g., $1.32T, $415.2B, $8.5M)
• Percentages: 2 decimal places with sign (e.g., +3.64%, -1.23%)

Rate Limits

For Pro/Analyst/Lite plans, query the /key endpoint for live quotas (Pro base URL only — returns 401 on Demo):

curl -s "https://pro-api.coingecko.com/api/v3/key" -H "x-cg-pro-api-key: $COINGECKO_PRO_API_KEY"

Returns plan, rate_limit_request_per_minute, monthly_call_credit, and current_remaining_monthly_calls. Demo users should refer to the pricing page for current limits.

Approximate defaults (may vary):

If rate limited (HTTP 429), wait briefly and retry. Batch multiple coin queries into single calls using comma-separated IDs where possible.

Error Handling

Tier-Restricted Endpoints

Some endpoints return 401 (error code 10005) on the Pro base URL for lower-tier plans (e.g., Analyst) but work on the Demo base URL.

Known Analyst-tier restrictions (401/10005 on Pro base URL):

• /search/trending
• /global
• /global/decentralized_finance_defi

Fallback strategy: On a 401 with error code 10005, retry on the Demo base URL. If COINGECKO_API_KEY is available, use it for better rate limits; otherwise fall back to keyless:

if [ -n "$COINGECKO_API_KEY" ]; then
  curl -s "https://api.coingecko.com/api/v3/search/trending" \
    -H "x-cg-demo-api-key: $COINGECKO_API_KEY"
else
  curl -s "https://api.coingecko.com/api/v3/search/trending"
fi

Do not use this fallback for error code 10002 (invalid key) — that indicates a misconfigured API key, not a tier restriction.

Reference Files

• ./references/endpoints.md — Curated endpoint reference with parameters, response formats, and asset platform IDs
• ./references/platforms.md — Curated list of common asset platform IDs with chain mappings (query /asset_platforms for the full live index)

Fallback Documentation

For endpoints not covered by this skill (on-chain DEX data, NFT details, exchange-specific queries), fetch the AI-friendly documentation:

https://docs.coingecko.com/llms.txt

Use WebFetch to retrieve this documentation for extended API capabilities.