You can call
(mind the
true = verbose).
If you have to do multiple rpc calls, check out the JSON RPC 2.0 batching options (since bitcoind 0.7 aggregate multiple rpc calls in one). If you need more details check the bitcoin-core source and search after
static string JSONRPCExecBatch(const UniValue& vReq)
There is a pull request for mempool REST call (
https://github.com/bitcoin/bitcoin/pull/6013).