rpc: add optimal result to getmempoolinfo

diff --git a/src/rpc/mempool.cpp b/src/rpc/mempool.cpp
index 66ce1c61..d9e135b6 100644
--- a/src/rpc/mempool.cpp
+++ b/src/rpc/mempool.cpp
@@ -874,6 +874,7 @@ UniValue MempoolInfoToJSON(const CTxMemPool& pool)
     ret.pushKV("maxdatacarriersize", pool.m_opts.max_datacarrier_bytes.value_or(0));
     ret.pushKV("limitclustercount", pool.m_opts.limits.cluster_count);
     ret.pushKV("limitclustersize", pool.m_opts.limits.cluster_size_vbytes);
+    ret.pushKV("optimal", pool.m_txgraph->DoWork(0)); // 0 work is a quick check for known optimality
     return ret;
 }
 
@@ -900,6 +901,7 @@ static RPCHelpMan getmempoolinfo()
                 {RPCResult::Type::NUM, "maxdatacarriersize", "Maximum number of bytes that can be used by OP_RETURN outputs in the mempool"},
                 {RPCResult::Type::NUM, "limitclustercount", "Maximum number of transactions that can be in a cluster (configured by -limitclustercount)"},
                 {RPCResult::Type::NUM, "limitclustersize", "Maximum size of a cluster in virtual bytes (configured by -limitclustersize)"},
+                {RPCResult::Type::BOOL, "optimal", "If the mempool is in a known-optimal transaction ordering"},
             }},
         RPCExamples{
             HelpExampleCli("getmempoolinfo", "")
diff --git a/test/functional/mempool_cluster.py b/test/functional/mempool_cluster.py
index 921f7441..6fe38771 100755
--- a/test/functional/mempool_cluster.py
+++ b/test/functional/mempool_cluster.py
@@ -306,6 +306,9 @@ class MempoolClusterTest(BitcoinTestFramework):
 
         assert_equal(node.getrawmempool(), [])
 
+        # Key should exist and be trivially optimal
+        assert node.getmempoolinfo()["optimal"]
+
         # Not in-mempool
         not_mempool_tx = self.wallet.create_self_transfer()
         assert_raises_rpc_error(-5, "Transaction not in mempool", node.getmempoolcluster, not_mempool_tx["txid"])
@@ -367,6 +370,9 @@ class MempoolClusterTest(BitcoinTestFramework):
         chunkfee = first_chunk_tx["fee"] + second_chunk_tx["fee"] + third_chunk_tx["fee"]
         assert_equal(first_chunk_info, {'clusterweight': first_chunkweight + second_chunkweight + third_chunkweight, 'txcount': 3, 'chunks': [{'chunkfee': first_chunk_tx["fee"], 'chunkweight': first_chunkweight, 'txs': [first_chunk_tx["txid"]]}, {'chunkfee': second_chunk_tx["fee"], 'chunkweight': second_chunkweight, 'txs': [second_chunk_tx["txid"]]}, {'chunkfee': third_chunk_tx["fee"], 'chunkweight': third_chunkweight, 'txs': [third_chunk_tx["txid"]]}]})
 
+        # We expect known optimality directly after txn submission
+        assert node.getmempoolinfo()["optimal"]
+
         # If we prioritise the last transaction it can join the second transaction's chunk.
         node.prioritisetransaction(third_chunk_tx["txid"], 0, int(third_chunk_tx["fee"]*COIN) + 1)
         first_chunk_info = node.getmempoolcluster(first_chunk_tx["txid"])