UPDATE
The Compound cToken API now returns the values for you. See comp_borrow_apy and comp_supply_apy when requesting https://api.compound.finance/api/v2/ctoken
OLD METHOD:
- Pick a supported cToken and its underlying asset
- Query https://api.compound.finance/api/v2/governance/comp
- Take the value for
supplier_daily_comporborrower_daily_comp