I tested the $PYTH Pyth Playground with BTC/USD and SOL/USD using the shared demo-token flow.

The API Key field says it can be left empty to use a rate-limited demo token, but pressing Run with the field empty returns:

“Invalid API key. Check the key you pasted and try again.”

I reproduced this twice, including after a hard refresh.

For a new developer this is confusing because the UI explicitly suggests that no API key is required for testing. It would be better either to fix the demo-token fallback or show a clearer message if the shared demo token is temporarily unavailable or rate-limited.