  "mempoolminfee": 0.00000000

When the minrelaytxfee is > 0.

{
    UniValue result(UniValue::VOBJ);
    result.push_back(Pair("hash", blockindex->GetBlockHash().GetHex()));
    int confirmations = -1;
    
    if (chainActive.Contains(blockindex))
        confirmations = chainActive.Height() - blockindex->nHeight + 1;
    result.push_back(Pair("confirmations", confirmations));
    result.push_back(Pair("height", blockindex->nHeight));
    result.push_back(Pair("version", blockindex->nVersion));
    result.push_back(Pair("versionHex", strprintf("%08x", blockindex->nVersion)));
    result.push_back(Pair("merkleroot", blockindex->hashMerkleRoot.GetHex()));
    result.push_back(Pair("time", (int64_t)blockindex->nTime));
    result.push_back(Pair("mediantime", (int64_t)blockindex->GetMedianTimePast()));
    result.push_back(Pair("nonce", (uint64_t)blockindex->nNonce));
    result.push_back(Pair("bits", strprintf("%08x", blockindex->nBits)));
    result.push_back(Pair("difficulty", GetDifficulty(blockindex)));
    result.push_back(Pair("chainwork", blockindex->nChainWork.GetHex()));
    if (blockindex->pprev)
        result.push_back(Pair("previousblockhash", blockindex->pprev->GetBlockHash().GetHex()));
    CBlockIndex *pnext = chainActive.Next(blockindex);
    if (pnext)
        result.push_back(Pair("nextblockhash", pnext->GetBlockHash().GetHex()));
    return result;
}
UniValue blockToJSON(const CBlock& block, const CBlockIndex* blockindex, bool txDetails)