Spot token price in USD on OP Mainnet, read from SushiSwap and Uniswap v3 fee tiers pools at call time. Returns priceUsd, the routed pair, backing liquidityUsd, confidence and blockNumber. Requires ?symbol=TICKER (e.g. OP) or ?token=0xADDRESS. Errors: 400 missing_symbol|unknown_token, 404 no_reliable_price when pools are too thin, 502 upstream_read_failed. Depth is /liquidity; a size-aware quote is /slippage. Chain-pinned; bare /price = BSC.