Specifically, it adds an address into the wallet.

Easy to test now thanks to https://github.com/bitcoin/bitcoin/pull/14410
```
diff --git a/test/functional/wallet_importmulti.py b/test/functional/wallet_importmulti.py
index 9ba6860..bff37b2 100755
--- a/test/functional/wallet_importmulti.py
+++ b/test/functional/wallet_importmulti.py
@@ -95,6 +95,7 @@ class ImportMultiTest(BitcoinTestFramework):
         assert_equal(address_assert['iswatchonly'], True)
         assert_equal(address_assert['ismine'], False)
         assert_equal(address_assert['timestamp'], timestamp)
+        assert_equal(address_assert['ischange'], True)
 
         # ScriptPubKey + internal + label
         self.log.info("Should not allow a label to be specified when internal is true")
```

throw JSONRPCError(RPC_WALLET_ERROR, "The wallet already contains the private key for this address or script");
                }
                pwallet->MarkDirty();
                if (!pwallet->AddWatchOnly(scriptRawPubKey, timestamp)) {
                    throw JSONRPCError(RPC_WALLET_ERROR, "Error adding address to wallet");
                }
            }
        }
        
        if (::IsMine(*pwallet, scriptpubkey_script) == ISMINE_SPENDABLE) {
            throw JSONRPCError(RPC_WALLET_ERROR, "The wallet already contains the private key for this address or script");
        }
        pwallet->MarkDirty();
        if (!pwallet->AddWatchOnly(scriptpubkey_script, timestamp)) {
            throw JSONRPCError(RPC_WALLET_ERROR, "Error adding address to wallet");
        }
        if (!watchOnly && !pwallet->HaveCScript(CScriptID(scriptpubkey_script)) && !pwallet->AddCScript(scriptpubkey_script)) {
            throw JSONRPCError(RPC_WALLET_ERROR, "Error adding scriptPubKey script to wallet");
        }
        
        if (IsValidDestination(scriptpubkey_dest)) {
            pwallet->SetAddressBook(scriptpubkey_dest, label, "receive");
        }
        
        for (size_t i = 0; i < keys.size(); i++) {
            const std::string& strPrivkey = keys[i].get_str();
            
            CKey key = DecodeSecret(strPrivkey);
            if (!key.IsValid()) {
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid private key encoding");