Query real-time stablecoin supply yield pools from Barker's index of 500+ DeFi protocols. Returns ranked rows with protocol_name, chain_name, asset_symbol, supply_apy_total (decimal — multiply by 100 for %), and supply_tvl (USD). Use for questions like 'best stablecoin yield', 'where to earn on USDC', 'compare lending rates', '稳定币利率'.

Stablecoin market snapshot: total market cap, yield-bearing cap, asset distribution, chain distribution. Use for 'stablecoin market cap', 'USDT market share', '稳定币市场份额'. share_pct fields are decimals (0.425 = 42.5%).

Historical APY trend for stablecoins vs. US Treasury benchmark over a lookback window (7–180 days). Use for 'DeFi vs treasury', 'is stablecoin APY going up', 'crypto yield trend', '稳定币利率走势'.

Agent-economy payment metrics from Barker's cross-protocol index. x402 (Base) is on-chain verifiable; Virtuals ACP, Google AP2, Stripe-Tempo MPP, OKX MPP, and Mastercard AP4M are self-reported claims. Separates real vs nominal volume by filtering out wash/noise sellers (avg_tx_usd < $0.02 with a very high tx-per-buyer ratio). Three views: 'summary' (hero KPIs + cross-protocol comparison table), 'trend' (daily tx / nominal & real volume / buyers), 'leaderboard' (top x402 sellers/endpoints by revenue). Use for 'x402 volume', 'agent payment stats', 'agent economy metrics', 'how big is x402', 'top x402 sellers', 'real vs nominal agent GMV', '智能体支付', 'x402 交易量'. All *_share_pct and noise_share_pct fields are percentages (77.0 = 77%); volume fields are USD.