commentary around the little-endian situation

consensus-types/blocks/get_payload.go

@@ -41,6 +41,10 @@ func NewGetPayloadResponse(msg proto.Message) (*GetPayloadResponse, error) {
 	bidValueGetter, hasBid := msg.(bidValueGetter)
 	wei := primitives.ZeroWei
 	if hasBid {
+		// The protobuf types that engine api responses unmarshal into store their values in little endian form.
+		// This is done for consistency with other uint256 values stored in protobufs for SSZ values.
+		// Long term we should move away from protobuf types for these values and just keep the bid as a big.Int as soon
+		// as we unmarshal it from the engine api response.
 		wei = primitives.LittleEndianBytesToWei(bidValueGetter.GetValue())
 	}
 	r.Bid = wei

consensus-types/primitives/wei.go

@@ -72,6 +72,9 @@ func Uint64ToWei(v uint64) Wei {
 }
 
 // LittleEndianBytesToWei returns a Wei value given a little-endian binary representation.
+// The only places we use this representation are in protobuf types that hold either the
+// local execution payload bid or the builder bid. Going forward we should avoid that representation
+// so this function being used in new places should be considered a code smell.
 func LittleEndianBytesToWei(value []byte) Wei {
 	if len(value) == 0 {
 		return big.NewInt(0)