Get the best vault APY for a token on Morpho Blue protocol. Only returns Morpho-curated vaults (excludes unlisted/test vaults). Requires a token contract address. Omit chainId to search all supported chains at once. Supports minApyPercent and limit filters for targeted vault discovery. Supports Ethereum (1), Optimism (10), Polygon (137), Base (8453), Arbitrum (42161). Ideal for: yield optimization, vault discovery, APY comparison, DeFi strategy selection, cross-chain yield alerts.