https://api.stynar.comEvery request against this base URL runs against real account data — there's no separate sandbox mode for the API today, so requests made here have the same effect as the equivalent action in the Stynar app.
Without a sandbox, test with real-but-low-stakes data: create a campaign with your own email as the only lead, or use a key with only the read scope while you're exploring GET endpoints. See API Keys for scopes.