# Providers & symbol formats

## Stocks / ETFs / Indices (default: Yahoo via yfinance)
Pros:
- Very broad symbol coverage, no API key.
Cons:
- Unofficial access patterns can be rate-limited or break.

Common examples:
- AAPL, MSFT, TSLA
- Indices: ^GSPC (S&P 500), ^DJI, ^IXIC
- ETFs: VOO, SPY, QQQ

## FX (default: ExchangeRate-API Open Access)
Endpoint: https://open.er-api.com/v6/latest/<BASE>
- No API key
- Updates once per day
- Rate-limited
- Attribution required by their terms

Symbol formats accepted by this skill:
- USD/ZAR
- USDZAR
- GBP-JPY
- EURUSD

We normalize to BASE/QUOTE and fetch BASE->all then pick QUOTE.

## Why not exchangerate.host by default?
It now requires an API key for most useful endpoints and has limited free quotas, so it’s not a great no-key default.

## Paid providers (optional future upgrade)
If you need many symbols or frequent polling:
- Twelve Data
- Alpha Vantage
- Polygon
- Finnhub

This skill includes environment variable placeholders, but does not implement these providers yet.