Base (chain 8453) gas tip for agents that send transactions: latest block number and age, base fee, eth_gasPrice, eth_maxPriorityFeePerGas and a suggested maxFeePerGas (2x base fee + priority), from one batched RPC call every 2 s. Long-poll with ?since=<seq>&wait=25. Prepaid meter price $0.0002/call (packs at /v1/meter); SSE at /v1/stream/tips.